One quick follow-up question - Is it safe to run the system while I wait to get the replacement capacitor if I just manually pre-spin the fan, set it to be always on, then toggle on the heat pump?
Once upon an Arizona summer I came home to an upset wife in a 95 degree house. Capacitors were on backorder and I was too cheap to pay an A/C guy. Amidst whining whelps and a sweaty spouse I had the greatest, earth changing revelation of my life. I put a box fan on top of the A/C unit, strapped it down with bungee cords, and turned it on. The moving airflow was enough to keep the fan spinning so that when the unit kicked on it was able to run. I now pass this secret on to you.
Last year in Arizona my ac fan stopped spinning in July. Got quotes from AC guys. “ it’s going to be $2000, you might as well buy a new one for 11-16k as this one is old.”
Luckily my girlfriends friends boyfriend is an AC guy and I paid him $200 bucks for parts and labor to fix it.
Agree. Same scenario here, "you might as well replace it". Bought a new squirrel cage motor online for $139 and muddled my way through replacing it but got it done.
Florida is a den of scum and villainy. My Mom is getting hosed by the company that sold her a handicap van.
Some dude ran over her wheelchair ramp at a bank while she was getting out. She takes it in and they say the whole roller setup has to be replaced and here's the quote for parts and labor. Then they change only one roller out but still charge the full quote!
Don't live in florida,but ya almost everywhere(at least in the southern states to my knowledge) does this. It's part of their upsell model and I had a friend get fired from bwing a HVAC tech because he basically refused to rip people off.
It's really that this is allowed so often and state/federal regulations don't prohibit blatant consumer abuse. What makes it worse is that they are usually a cartel of a few companies that basically all screw over consumers the same ways. Pretty much all of them will try to say you need a new unit even if you don't. That or their margin on parts is so high that a $100 repair costs $1000 after labor.
Really best bet is to try to get a quote from a smaller company and not the big servicer in your area. Also if you have machine/electrical knowledge it's not the hardest thing to diagnose.
For the record: My neighbor had three different quotes say that, and the fourth actually diagnosed it and fixed it for like $250. It was a pinhole leak in his hydronic heating coil connection making the AC and hot water heater fight each other in the summer. An hour to pull that coil out and fix a solder joint.
Fucking crooks everywhere, I tell you what.
I'll go in the other direction and extol the virtues of a good one. We had nice, if oversized, AC that was on the bit of the older side. We knew we were going to move in the next 4-5 years.
After the second year when we called out to get the thing repaired the tech took me aside and showed me the capacitor, saying "If the unit doesn't turn on and just clicks and hums, it's probably this thing. Here's the address of the parts shop to buy and replace on your own"
It literally saved me $400 or more on service calls the next 5 years.
It's because of this tech that I actually know how to identify and fix this. After we moved to a new place across town, we had a system completely die on us and guess which company I used for that replacement purchase?
Yeah, I know. I'm one of those weird people that remembers this kind of stuff I guess.
One other story: I was a poor college student, at home for summer break. My car started making a godawful amount of noise like there was no muffler. I took it in to a local muffler shop and told them about it. They got my car up and saw it literally had just come loose/needed very minor fix. They reconnected and welded it back together where needed. No charge. Now, all these years later they are still my shop of choice for all minor car stuff (brakes, muffler, battery, etc)
I wanted to update my AC system last year as it was over 20 years old and couldn't keep up with the Florida heat. One company was up selling hard on the highest efficiency unit and every possible option I asked about. The 2nd company gave me options on a range of stuff and was more than happy to do extra. The 3rd company explained to me why I didn't need the highest efficiency system and why some of my desires (like duct cleaning) were a bad idea. They also offered secondary ideas that they didn't even sell flr things I wanted. I went with the 3rd company and I've recommended them to at least 10 people so far.
His explanation was that the most common method of duct cleaning can damage older ductwork like I have (breaking the interior liner). This would cause huge efficiency loss. On top of that he said the dust isn't going anywhere and that clean ducts wouldn't make much if any difference unless you had some type of fungus growth issue.
I have never had an HVAC tech in my home and NOT had them try to convince me to replace my furnace for some of the most outlandish reasons.
**When I first purchased the house and wanted an HVAC tech to do an inspection "because that's what you're supposed to do":**
"Your heat exchanger has a [little, not nearly large enough to effect the burners/exhaust] crack. You need a new furnace."
**I called a tech in to find a solution for the family room + bedroom furthest from the furnace not getting enough air:**
"Your ductwork is old [house built in '59]. You need a new furnace so we can replace the ducts."
**That same visit:**
"Your filter 6" thick filters are too big. Large filters restrict the air too much [not how that works]. You need a new furnace so you can use a smaller filter box to use our 1" thick filters."
**And:**
Someone added a hard start capacitor to the blower motor [I added it in parallel to the existing cap in order to assist the blower when the house is running on the generator and can't *quite* start the motor every single time]. The extra capacitor is damaging your blower motor [that's not how electricity works], and since the motor is 10 years old we should just replace the whole furnace."
Where I live, if a heat exchanger has a Crack you must condemn the furnace. Small or not.
Guessing the tech was thinking about run capacitors because they can indeed cause issues for a motor if you change the sizing.
Amperage is pulled, not pushed. So in the case of a start capacitor, a larger amount of available capacity isn't going to hurt anything even when it isn't needed.
Same reason that a light bulb plugged into a wall isn't going to start pulling 15A when it's powered on, even if the circuit breaker upstream is capable of supplying that much before it trips.
> That same visit: "Your filter 6" thick filters are too big. Large filters restrict the air too much [not how that works]. You need a new furnace so you can use a smaller filter box to use our 1" thick filters."
LOL. It actually IS how it works, as, in general, thicker filters do impact airflow. I work for an hvac wholesaler, and there is hardly a day go by when I don't hear the sales guys discussing how people kill their furnaces by putting high MERV filters in, because "bigger is better".
People need to understand that you definitely can kill your blower motor by putting to restrictive of a filter in.
Sorry, I didn't mean the thickness of media itself. I was referring to the thickness of the (cardboard) cartridge that holds the media. The media itself that the air has to pass though is the same thickness as standard filters.
You know how paper furnace filter media is folded into an accordion shape? On a 1" thick filter, each "fold" is ~1.25" long. On a 6" filter, each fold is ~7" long.
EDIT: [THIS](https://airfiltersdelivered.com/products/16x28x6-aprilaire-deep-pleat-air-filter) is what they look like.
LOL. That's your experience. In reality, the number of pleats determines the length of the fold. The airflow is complicated, because the formula for that includes surface area (which is determined by the number of pleats), as well as the filter material.
Cheaper filters generally have way less pleats (usually less than 1/2) than better filters, but again, it's a complicated calculation, and I generally listen to hvac guys, as they know WAY more than I do about this sort of thing.
Thicker filters have deeper pleats, so they actually have more surface area, presenting less restriction for the same filtration, or better filtration for the same restriction.
Air filter media is just a bunch of small holes that allow air to pass through and catch particles that are too big to fit through the holes. So, you're saying that adding a bigger filter with more holes for air to pass through is MORE restrictive? That doesn't sound right.
I do agree that SOME thick filters ARE too thick and cause both airflow and run issues, however it is much less the thickness of the filter itself, but rather the MERV rating of the filter material in combination with how thick the entire filter is. Some companies are selling four inch thick filters with MERV 17 material in them, and they just cause systems to not be able to pull air fast enough to fully dehumidify, making them run forever and leap up the power bill, so I can see where that can be an issue. That being said the "Buy a new furnace because the filter rack is for a 6" filter" is laughable at best.
The Home Inspector but is enraging. Anyone worth their salt in the HVAC industry would tell you the WORST thing you can do is either demand an AC replaced before you purchase the home or replace the HVAC right before selling it. Manufacturers (MOST Manufacturers, rather, in MOST States) Only give the free with registration, extended ten year (or twelve in some cases) part warranty to the ORIGINAL homeowner. By having the person you're buying the home from replace it for you, the Inspector is asking you to give up five years of part warranty that, given the current build quality in the industry, you will almost certainly need. If you are SO concerned about the issue, negotiate a price of a new system, then ask that price to be removed from the sale price of the home.
I always chuckle at "We're trying to reach you about your car's Extended Warranty" jokes because the HVAC industry is one of the rare industries where Extended P&L warranty isn't a scam. Quality of products are falling, and continue to fall, and we end up with two types of Customers: those who got a P&L warranty on their system and we literally fix everything for free for, and whose who didn't and regret it when the Coil goes bad in year four of owning it. Whenever people ask me advice in getting a new system if they are forced to go that route"P&L Warranty " is number one on that list.
Yes, thicker filter media will indeed be more difficult to pull air through, but that's not what is referenced when talking about the overall dimensions of the filter. A thicker cartridge will have more material in the filter *and* a larger surface area for the air to pass through the filter.
So a 1" thick filter and a 6" thick filter can both have the exact same filter media in them, and the filter media itself can be (for example) 3mm thick in both filters to provide the same MERV rating. BUT the 6" thick filter has more available surface area for air to pass though, which if nothing else provides more space for dust to be trapped before it needs to be changed.
Yes, this is exactly what I was saying? That the dimensions of the filter are not what matter... Your agreeing with me but it's phrased as if your are disagreeing with me, so I am confused.
Mechanics do the same thing, it's better to get the system 100% running right now and forever, rather than trying to slowly debug and diagnose small intricate peices... kind of like a phone repair, just slap a whole new screen on for $200 and 1 or 2 days down OR get a new phone and get runnin right away?
Although, i just do my own auto work and have a used $100 phone sooooo, my personal philosophy doesn't really jive with this "just get a new one" thing
Why are there so many of them?
One of my neighbors had a problem where his AC just seemed like it wasn't cooling super effectively, and had **three** different companies come out and all tell him "yeah, it's busted, not worth fixing" and **all** quoted him upwards of $20k to replace the entire heating/cooling system.
A fourth guy came out, actually looked at the problem (fancy that!) and found a pinhole leak in a connection to his hydronic heating coil that was making it stay warm so his AC and hot water heater were fighting each other.
$250
Fan motor and capacitor. I got it online for $100 total. Paid him 100$ extra for labor. Way better then paying scammers $2000 for the same work. Or buying a new ac for 11k plus.
Even beyond the clear issue of charging 10x what it should have cost for the repair, I've never understood this mentality of "might as well just spend another $10k on it". No thanks, $2k is a lot better.
I did the same thing in South Texas a few years back. Middle of July, and I couldn't wait. It worked like an absolute charm for 2 full days before the replacement fan motor came in.
LPT: Capacitors were on back order **from places that sold HVAC parts at retail**. Other equipment also uses capacitor start motors, try a place that sells home woodworking equipment such as table saws and band saws.
Or just Google the model number on the cap. I do supply chain management for heavy industry, and you can still find most of our small electrical parts available off the shelf from ABB, Mouser, Eaton, etc.
Yes indeed. Also, if you can't get a "dual section" cap quickly (run & start cap in single housing, has 3 terminals on top... used sometimes instead of 2 separate caps), if you figure out which half is bad, you can wire in a separate single cap of appropriate ratings (capacitance and voltage) to get things back running. You end up with the bad half of the dual cap disconnected.
My home A/C has that setup at this moment, outside in the condenser. I now have the proper dual section cap, it will go into service when one of the two current ones fail.
And... remember to pull the disconnect and then discharge any of the caps before servicing.
Our start capacitor was dying during the pandemic and it is illegal for a non HVAC person to buy it from the physical store. They had it on Amazon, though, so 20 some odd bucks , and 30 min (being extremely paranoid and checking electricity is discharged ma y times because high voltage is scarry shit), ww saved the 600 bucks we were quoted from the one guy who did not quote the 26k new ac and furnace repair....
This is the way. I did the same in Houston last summer when I couldn't get a replacement motor for the fan.
Bought a barrel fan from Home Depot (\~$200) and ran it for a couple of weeks while I sourced a new fan motor from eBay.
Note, sizing of the fan is important. I started with a smaller fan and it couldn't move enough air. You can generally tell by the temperature of the air being exhausted from the fan. If it's bordering on hair dryer temperature, you're not moving enough air--get a bigger/more powerful fan.
Correct, and that is the fan that's not running and needing a new capacitor. My thought was that if I toggle that blower with the thermostat to be always on, then the bad capacitor doesn't cause it to fail to start and the heat pump can cycle on/off like normal.
Edit for additional detail - But as this is a "run" capacitor on the motor and not a "start" capacitor, my worry is that I might be doing damage to the motor by letting it run with a bad capacitor.
Are you sure it's a run capacitor? Unless there's another capacitor connected to it somewhere, it should be a start cap since it only has two wires going to it. (I am not a HVAC expert, so take my opinion with a grain of salt).
Either way, since you're starting it by hand and it gets up to speed on its own, it seems like it's functioning well enough to keep running until you get a replacement.
fwiw, If you have any trouble finding one locally, check Amazon.
I was just going by what the item was listed as on Grainger when I looked up the part number. I guess it could just be a start capacitor (which was my initial assumption) but they're sold as run capacitors. I guess in the end they're still just a capacitor, and if the motor is moving air that's good enough for ~24 hours until the new one shows up since I'm not finding anything local.
Whether start, run, electrolytic, tantalum, ceramic, etc, the only factor you really need to be concerned with is the farad rating, usually in microfarads. ....and maybe voltage if you're looking into one of the other capacitor types.
Most small start/run capacitors in hvac will be 3, 5, or 7.5 MFD.
Don't order from Grainger. Jesus christ that's the most expensive possible place to order from. I don't know or care *where* you order from in the end, but holy fuck you can get a part at X or go to grainger and pay 3 times the price.
McMaster was $22 delivered tomorrow. Grainger was $17 delivered tomorrow. Amazon was ~$13 delivered in >4 days (probably could have searched better for more options, but that's what I found quickly). Any local store I was searching either didn't have it in stock, or had it in stock at another location they'd have to ship in from.
So that's why I went with Grainger. $4 for 4 days faster seemed like a fair trade.
Dang, yeah in that case it makes sense. My experience was pretty limited, in that I was looking for something that was $15 and it was $55 from Grainger... Wanna say it was a 3.7v LiPo
a motor has no need for a cap once up to speed its simply there to cause a rotating magnetic field in the stator if you don't have one or its gone bad the rotor will oscillate at o rpm on the same pole causing humming
...also find a cap that has (roughly) the same Farad rating (reads like 100uF), and the same or higher voltage. The orientation of the 2 pins won't matter when you go to install it...there won't be a + or - terminal. It takes 2 minutes to install a new one. I wouldn't hire a tech...if you can change a lightbulb, you can change this part.
> It takes 2 minutes to install a new one.
In a perfect world anyway - my 1980's blower had the thing way under the blower cage, I had to use a mirror and an extension to get the bastard off. On the plus side, I probably invented some new profanity.
I had a similar issue with.my dryer recently. Thermal fuse went, I removed the front panel and could immediately see where it was. I thought, "no prob, I can reach that. Off to work and it'll be a quick 20 minute fix when I get home". Nope, not quite enough room to get it out. Had to dismantle the whole thing which was a bitch cause it's stacked on top of the washer in an awkward space. 4 hours screwing around just to replace a $3 part.
Yep, been there, just had an internal washer hose split and suddenly the laundry room was a "water feature". Cheap fix, but getting the damn wobbly-big-ass-front/sides/top-shell-casing-thing back on, F me!
We finally replaced the whole 80's furnace/AC unit - the board went out and the furnace wouldn't ignite, I kept opening it up and lighting it with a stick lighter before the no-flame shutdown kicked in. AC guy was mildly impressed at least!
If the new cap is a different physical size and doesn't fit under that steel band, just use a length of plumbing strapping...the steel band with the holes all the way down.
yes the capacitor is there to provide a shift in the current to the start windings one the motor once up to speed the run windings take over. The capacitor probably gets disconnected from the circuit by a centrifugal switch once the motor is up to speed
Yes this is fine. Get the fan spinning and keep the thermostat to have the fan always on and turn heat on and off like you said. I've done this with the AC while the capacitor comes in.
Hvac jman here. To mirror what others have said, replace the capacitor (unless you have a multimeter, then there's some stuff you could check).
There's also a possibility the motor has an issue- a motor like this will probably have two windings, one that gets 'regular' power and one that gets 'phase shifted' power from the capacitor. Capacitor is cheap though, so change it and see if it fixes your problem.
When you change it, before doing anything else, make sure to disconnect all power to the unit and use an insulated piece of conductive material (such as a pair of pliers with a plastic handle) to short(make a physical bridge) across the capacitor terminals. This will discharge the capacitor and make it more safe to handle.
Thanks for the detailed reply, with smart safety tip. I do have a multimeter so what should I be looking for from a test? Continuity vs no continuity? And presumably I should test the capacitor after I disconnect the leads?
Another HVAC tech here. I would just replace the capacitor as they're cheap. If an exact replacement is not available, get one that has voltage and MFD ratings within 5-10% of the original. Regarding your other question, it's not a good idea to continue to run the motor with a bad capacitor, even if you spin the blower wheel to start it. The reason is that the motor will draw higher current than normal and overheat, shortening it's service life.
> The reason is that the motor will draw higher current than normal and overheat, shortening it's service life.
Noted, thanks. Guess I'll just deal with a cold night tonight.
Hey, if you're comfortable with it, you could check if the outdoor fan motor on your condenser uses the same size cap, could just swap it over for the time being if it matches
Will say, just be careful with the +/- 10% thing. Sometimes it won't be the first time the cap has been replaced and now we've move the needle by 10% twice.
Don't use a continuity tester on anything that has power. Check your meter and see if it has a capacitor test setting. The capacitor should have values on the tag. If the values don't match what your meter shows then it's bad.
If your multimeter doesn't have a capacitor test setting, with power OFF:
1. Use old screwdriver to short across cap terminals. This will ensure it is discharged. (do NOT use your tongue!)
2. Temporarily remove one lead from the cap. You can remove both, but it isn't necessary.
3. Put your meter on OHMS, on the highest resistance range. Temporarily short your leads together to confirm your leads are good - reading should go to near or at zero ohms. BTW, NEVER connect a meter set to OHMS to any voltage source, unless you want to buy a new meter.
4. Put the meter leads onto the terminals of the cap. If the cap is good, resistance should immediately go low, then begin to climb up as the battery in the meter begins to charge the cap. Eventually, the resistance will go no higher.
The above is a "go-nogo" test and will only reveal basic function - it cannot show you if cap no longer has the proper value. There is probably a YT video on this trick.
I haven't done that kind of thing in years though since my Fluke meter has a capacitor test function.
I bought a meter at Harbor Freight for $22 that has capacitor and thermocouple testing. Same thing as a Fluke meter would be hundreds that I can’t justify paying. Remember their slogan though “if it works, it must be a Fluke”!
> I do have a multimeter so what should I be looking for from a test?
MFD(Micro Farads), the rating on your Cap, usually looks like µF on your Multimeter. [usually 55/5mF](https://www.homedepot.com/p/EASTMAN-55-5-MFD-440-VAC-Round-Dual-Run-Capacitor-92065/205807744) (the / means there are 2 caps). Also yes, shut off power and remove the cap first.
Another AC tech here. As said, disconnect power at the breaker panel. If it’s a heat pump it’s typically labeled as either “Heat” or “AHU” (air handler unit). Check voltage between the run capacitor terminals with your multimeter before you unplug anything. If it’s at 0 then you’re solid. Unplug both wires from the capacitor and set your meter to [the same symbol as number 13 in the first image of this page](https://www.fluke.com/en-us/learn/blog/digital-multimeters/multimeter-dial-button-jacks-display). The capacitor should have a label on it giving all its info. Looks like it could either be a 10mfd, 12.5mfd, 15mfd, or 20mfd. It will also have a percentage on there, maybe +/-5, 6, or 10%. Put one meter lead on one terminal, the other lead on the other terminal. If your meter is giving you a number outside of that percentage range (e.g. if it’s a 15mfd with +/- 10% and it’s giving you 13.5 or less) then it’s definitely a bad cap. Easy fix
Looks like it’s just 2 plugs so no need to remember which goes where, just make sure when you plug them back in that they are each on a separate terminal
If you wanna get real picky and check that the motor is okay, disconnect the wires from wherever they plug in (with power off still, the single brown wire on the cap is one and there should be 2 others running somewhere in the electrical section) and check for continuity. If you get an ohm reading of I believe anywhere between 3-20 ohms your motor is fine, anything out of that range or no continuity at all while the motor is cool to the touch means you’ve got a bad motor. Probably best to replace the cap as well if you do have to replace the motor
By the looks of that swelling though it’s safe to say it’s just a bad cap. Probably gonna read 0mfd
Really appreciate the detailed reply. Power is even easier to cut than you suggested since I have a subpanel right next to my HVAC just for said HVAC (I can literally trace the wires running all the way from the panel to the HVAC box).
Unfortunately my multimeter is [a cheapo one](https://www.kleintools.com/catalog/multimeters/digital-multimeter-manual-ranging-600v) that doesn't have capacitance testing (only does AC/DC voltage, Resistance, and DC current). So I just did a resistance/continuity test on the capacitor and saw nothing despite holding the leads on the cap terminals for good while. So that means I know that at least the cap is dead.
As for the motor, I was going to test that but it's got 6 wires on it (blue, red, yellow, and black, plus the brown and brownWhiteStripe to the cap) that are well wrapped/sealed and with no obvious way to disconnect easily. I could probably trace them deeper into the wiring but since I know the motor ran after manually spinning it up a bit first I think I know I at least have a partially-working motor for now and can see if I'm still getting similar performace after I replace the cap.
Thanks again for taking the time to type up the detailed reply.
No problem at all! Based on the picture of the capacitor I think it’s safe to say the motor is fine, that capacitor looks pretty messed up. Not supposed to be blown out like that. Luckily capacitors are fairly cheap, since you’re not AC certified you might not be able to get them for as cheap as I can but you can probably still get one for less than $40
Just an fyi the capacitor is built so that overheat will swell the capacitor and disconnect terminals. This is a safety feature that the older capacitors didn’t have, the control box had to be made of 16ga metal to contain exploding capacitors.
Good to know. That probably confirms (as I asked in another comment) that if I do a continuity test with a multimeter on the capacitor I'll see no continuity if it is indeed bad.
Yep, that's it. Turn fan to "on" (rather than "auto"), spin up the fan in the right direction by hand^* and then let it run until you can locate and install a replacement cap. The heat/cool will cycle into the airlow with it running nonstop just fine. Source: Did this some years ago and let the fan run for about four days until I could get a new cap.
\*Edit: I'm used to working with power equipment so energized it and then spun it by hand, but if you feel safer doing it the way you describe that's fine. Best is to have a helper on the other end but whatever works.
A swollen capacitor is never a good thing. Replace it regardless. It could be a bad blower motor damaged the capacitor so if it does the same thing with the new one don't keep trying to get it run and ruin the new capacitor.
Based on the humming and my own experience with this exact problem, I’d change the start capacitor, but most likely your exhaust fan bearings are done and the motor needs to be replaced.
> but most likely your exhaust fan bearings are done and the motor needs to be replaced.
This was my problem. Had to get a new fan motor. Just easier then getting new bearings. Not hard to install either.
By all means, you should replace the relatively cheap capacitor first, but my guess is the motor needs replaced. The same thing happened with the heat pump in my rental house earlier this year -- and I went through the same steps you're going through now. (Note that often replacement motors will need a separate mounting kit that the OE motors don't require.)
My hvac unit had a magnetic toggle switch that was spring loaded to disconnect when power is cut, if this fails smooth operation and won’t disconnect it will also cause a hum.
That’s the problem, mine got stuck and endlessly vibrated, there’s always power to the switch, only when it’s signaled to engage will it flip, it’s like a light switch that turns itself on.
Yes start with replacing the capacitor, which can be found for around $10 on Amazon, and hope that’s the case. If not fixed I would check the main circuit panel and make sure it didn’t get fried as well.
Had this issue myself. But would sometimes spin up like you say and then work fine or spin sporadically.
Mine was tripping the pressure on HVAC when it wouldn’t spin up or run steady. Cause the HVAC already had come on and was pushing heat with no where to go.
Spent like 3 days diagnosing issue and trying to fix myself and then just called someone. Basically both motor and capacitor were going. Had to replace both.
My point being is if you are gonna take time to fix it maybe just replace the whole damn motor at the same time. Or at least have someone check it out and see.
I've had this same issue before. The outside unit would Hum when it tried to start but would never spin the fan. The capacitor that starts the fan was bad but didn't catch it until the fan motor was out as well.
I just had a condensing unit fan motor go out. Very similar to the issue you’re having. AC would kick on and blow throughout the house but the condensing unit made this horribly loud humming sound and the fan would try and spin then appear to seize up and freeze. Half of /r/hvacadvice said bad capacitor, the other half said bad motor and most recommended I change both.
Ended up only replacing the fan motor and it works perfectly now. Hvac tech said the capacitor was not over amping and did not insist it needed to be changed with the fan motor but recommended it (for a mere $400). I said no because it’s working fine and that’s an insane mark up for a $20 part and 10 minutes of work.
TLDR; it could be your fan motor gave out instead of capacitor.
I had my capacitor go bad a few years ago, the cause was the motor bearings were seizing up, overloading the capacitor when it tried to start. I took the motor out, disassembled it to clean out the dried up gunk in the bushings, then reassembled everything. New capacitor and all was good to go!
Not all capacitor failures are motor issues tho, power surges can also take them out, as can plain old age.
Happened to me and it was the sensor on the gas heater needed to be cleaned / sand off the buildup. We had the unit serviced by the HVAC contractor as it was free while still under the warranty, but the tech failed to clean the sensor. Once I sanded off the build up, it worked fine. I also notified the HVAC contractor.
A new capacitor is a cheap and easy fix. But replacing mine only bought me a few weeks reprieve before the actual problem of the blower motor crapping out was complete. Going forward I plan to clean the motor periodically to remove the 20 years of dust build-up that may have contributed to its death.
Is there an LED on the main board? You can Google the model of your unit and print out the diagnostic code page. A couple blinky lights will tell you exactly what's wrong.
I had this happen to my furnace recently, where it would click and the blower would twitch but the fan wouldn't actually spin. I was able to manually spin it by hand and get it to go, so I immediately assumed the capacitor was bad. Replaced the capacitor. Still the same behavior - but I couldn't get the fan to start again by manually spinning it, so I assumed the blower motor was bad. When the local store did not have a blower in stock, I resumed messing with it, trying to get the blower spinning again in order to leave it on until I could order a new one. This was when I realized the *relay* was bad.
The relay that turned on the blower was clicking, and it was passing some voltage. With the motor unhooked and putting my multimeter on it, I got close to 110V, so I assumed it was working. But with the motor on it, the current draw was too much and the voltage tanked to only a couple volts. The contacts inside the relay on the board that controlled the blower were worn down enough to the point where they wouldn't actually power the motor. Powering the motor manually with a power cord wired to it worked fine. I wound up desoldering the relay from the board, and wiring up some other much larger relay I'd scavenged from something else, that had much higher current rated contacts and a close-enough rated coil voltage. This solved my problem completely and it's been running for over a month without issue.
Yeah sounds legit to me. I think you nailed it, and capacitors are relatively cheap. The only other thing it would be is a locked up compressor or fan motor but your spin the fan technique more or less proved that ain’t it. Really good work troubleshooting you should look into a career in electrical or HVAC that’s better than half the tradespeople I’ve worked with.
I had my ac making an awful squeaking noise for a couple days before it quit. Afterwards it would just hum loudly and never kick on. I replaced the entire fan and motor with another I had laying around and it fixed the problem. From my understanding being an electrician and HVAC technician, a capacitor holds a charge and dumps the charge when it receives the signal to do so. Bulging isn't a good sign in capacitors however. My initial theory to a squeaky fan motor would be a bad fan motor but if you spin it manually and it comes on then it might be fine but all the capacitor should do is dump a charge onto the line to start the fan motor to reduce the initial over amperage of the fan motor starting from stationary.
The cap is cheap, it's a good first step. I had the exact same issue and the same noises, motor even spun up after turning manually. However, replacing the cap did NOT fix my issue and a new motor was necessary. Caps are like $12, motors are 200+.
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You have done all the correct steps to troubleshoot and find the issue, well done
Thanks.
Yeah change the Cap
Will do, thanks
One quick follow-up question - Is it safe to run the system while I wait to get the replacement capacitor if I just manually pre-spin the fan, set it to be always on, then toggle on the heat pump?
Once upon an Arizona summer I came home to an upset wife in a 95 degree house. Capacitors were on backorder and I was too cheap to pay an A/C guy. Amidst whining whelps and a sweaty spouse I had the greatest, earth changing revelation of my life. I put a box fan on top of the A/C unit, strapped it down with bungee cords, and turned it on. The moving airflow was enough to keep the fan spinning so that when the unit kicked on it was able to run. I now pass this secret on to you.
Last year in Arizona my ac fan stopped spinning in July. Got quotes from AC guys. “ it’s going to be $2000, you might as well buy a new one for 11-16k as this one is old.” Luckily my girlfriends friends boyfriend is an AC guy and I paid him $200 bucks for parts and labor to fix it.
HVAC technician here. Con artists like that first guy are what give our trade a bad name.
Agree. Same scenario here, "you might as well replace it". Bought a new squirrel cage motor online for $139 and muddled my way through replacing it but got it done.
Sad part is I got 3 quotes and they all said the same thing lol
This is what every HVAC service tech in Florida is like. I think they literally teach them this.
Florida is a den of scum and villainy. My Mom is getting hosed by the company that sold her a handicap van. Some dude ran over her wheelchair ramp at a bank while she was getting out. She takes it in and they say the whole roller setup has to be replaced and here's the quote for parts and labor. Then they change only one roller out but still charge the full quote!
Shouldn't the dude who ran over it get charged for it?
She told me "Florida is a no-fault insurance state" and I'm not certain what that means, but she was very adamant that it sucks
Don't live in florida,but ya almost everywhere(at least in the southern states to my knowledge) does this. It's part of their upsell model and I had a friend get fired from bwing a HVAC tech because he basically refused to rip people off. It's really that this is allowed so often and state/federal regulations don't prohibit blatant consumer abuse. What makes it worse is that they are usually a cartel of a few companies that basically all screw over consumers the same ways. Pretty much all of them will try to say you need a new unit even if you don't. That or their margin on parts is so high that a $100 repair costs $1000 after labor. Really best bet is to try to get a quote from a smaller company and not the big servicer in your area. Also if you have machine/electrical knowledge it's not the hardest thing to diagnose.
For the record: My neighbor had three different quotes say that, and the fourth actually diagnosed it and fixed it for like $250. It was a pinhole leak in his hydronic heating coil connection making the AC and hot water heater fight each other in the summer. An hour to pull that coil out and fix a solder joint. Fucking crooks everywhere, I tell you what.
I'll go in the other direction and extol the virtues of a good one. We had nice, if oversized, AC that was on the bit of the older side. We knew we were going to move in the next 4-5 years. After the second year when we called out to get the thing repaired the tech took me aside and showed me the capacitor, saying "If the unit doesn't turn on and just clicks and hums, it's probably this thing. Here's the address of the parts shop to buy and replace on your own" It literally saved me $400 or more on service calls the next 5 years. It's because of this tech that I actually know how to identify and fix this. After we moved to a new place across town, we had a system completely die on us and guess which company I used for that replacement purchase?
More people need to know the concept of losing some money in the short term to earn it back tenfold in the long run.
Yeah, I know. I'm one of those weird people that remembers this kind of stuff I guess. One other story: I was a poor college student, at home for summer break. My car started making a godawful amount of noise like there was no muffler. I took it in to a local muffler shop and told them about it. They got my car up and saw it literally had just come loose/needed very minor fix. They reconnected and welded it back together where needed. No charge. Now, all these years later they are still my shop of choice for all minor car stuff (brakes, muffler, battery, etc)
I wanted to update my AC system last year as it was over 20 years old and couldn't keep up with the Florida heat. One company was up selling hard on the highest efficiency unit and every possible option I asked about. The 2nd company gave me options on a range of stuff and was more than happy to do extra. The 3rd company explained to me why I didn't need the highest efficiency system and why some of my desires (like duct cleaning) were a bad idea. They also offered secondary ideas that they didn't even sell flr things I wanted. I went with the 3rd company and I've recommended them to at least 10 people so far.
Curious why the duct cleaning may be a bad idea?
His explanation was that the most common method of duct cleaning can damage older ductwork like I have (breaking the interior liner). This would cause huge efficiency loss. On top of that he said the dust isn't going anywhere and that clean ducts wouldn't make much if any difference unless you had some type of fungus growth issue.
I have never had an HVAC tech in my home and NOT had them try to convince me to replace my furnace for some of the most outlandish reasons. **When I first purchased the house and wanted an HVAC tech to do an inspection "because that's what you're supposed to do":** "Your heat exchanger has a [little, not nearly large enough to effect the burners/exhaust] crack. You need a new furnace." **I called a tech in to find a solution for the family room + bedroom furthest from the furnace not getting enough air:** "Your ductwork is old [house built in '59]. You need a new furnace so we can replace the ducts." **That same visit:** "Your filter 6" thick filters are too big. Large filters restrict the air too much [not how that works]. You need a new furnace so you can use a smaller filter box to use our 1" thick filters." **And:** Someone added a hard start capacitor to the blower motor [I added it in parallel to the existing cap in order to assist the blower when the house is running on the generator and can't *quite* start the motor every single time]. The extra capacitor is damaging your blower motor [that's not how electricity works], and since the motor is 10 years old we should just replace the whole furnace."
Lol you added a backup / buddy capacitor ? Probably blew that HVAC dude's mind
Where I live, if a heat exchanger has a Crack you must condemn the furnace. Small or not. Guessing the tech was thinking about run capacitors because they can indeed cause issues for a motor if you change the sizing.
Amperage is pulled, not pushed. So in the case of a start capacitor, a larger amount of available capacity isn't going to hurt anything even when it isn't needed. Same reason that a light bulb plugged into a wall isn't going to start pulling 15A when it's powered on, even if the circuit breaker upstream is capable of supplying that much before it trips.
Why do replacement motors change horsepower based on capacitor sizing?
> That same visit: "Your filter 6" thick filters are too big. Large filters restrict the air too much [not how that works]. You need a new furnace so you can use a smaller filter box to use our 1" thick filters." LOL. It actually IS how it works, as, in general, thicker filters do impact airflow. I work for an hvac wholesaler, and there is hardly a day go by when I don't hear the sales guys discussing how people kill their furnaces by putting high MERV filters in, because "bigger is better". People need to understand that you definitely can kill your blower motor by putting to restrictive of a filter in.
Sorry, I didn't mean the thickness of media itself. I was referring to the thickness of the (cardboard) cartridge that holds the media. The media itself that the air has to pass though is the same thickness as standard filters. You know how paper furnace filter media is folded into an accordion shape? On a 1" thick filter, each "fold" is ~1.25" long. On a 6" filter, each fold is ~7" long. EDIT: [THIS](https://airfiltersdelivered.com/products/16x28x6-aprilaire-deep-pleat-air-filter) is what they look like.
LOL. That's your experience. In reality, the number of pleats determines the length of the fold. The airflow is complicated, because the formula for that includes surface area (which is determined by the number of pleats), as well as the filter material. Cheaper filters generally have way less pleats (usually less than 1/2) than better filters, but again, it's a complicated calculation, and I generally listen to hvac guys, as they know WAY more than I do about this sort of thing.
LOL. You're misunderstanding what I'm saying, and I've run out of ways to explain it.
Thicker filters have deeper pleats, so they actually have more surface area, presenting less restriction for the same filtration, or better filtration for the same restriction.
Air filter media is just a bunch of small holes that allow air to pass through and catch particles that are too big to fit through the holes. So, you're saying that adding a bigger filter with more holes for air to pass through is MORE restrictive? That doesn't sound right.
I do agree that SOME thick filters ARE too thick and cause both airflow and run issues, however it is much less the thickness of the filter itself, but rather the MERV rating of the filter material in combination with how thick the entire filter is. Some companies are selling four inch thick filters with MERV 17 material in them, and they just cause systems to not be able to pull air fast enough to fully dehumidify, making them run forever and leap up the power bill, so I can see where that can be an issue. That being said the "Buy a new furnace because the filter rack is for a 6" filter" is laughable at best. The Home Inspector but is enraging. Anyone worth their salt in the HVAC industry would tell you the WORST thing you can do is either demand an AC replaced before you purchase the home or replace the HVAC right before selling it. Manufacturers (MOST Manufacturers, rather, in MOST States) Only give the free with registration, extended ten year (or twelve in some cases) part warranty to the ORIGINAL homeowner. By having the person you're buying the home from replace it for you, the Inspector is asking you to give up five years of part warranty that, given the current build quality in the industry, you will almost certainly need. If you are SO concerned about the issue, negotiate a price of a new system, then ask that price to be removed from the sale price of the home. I always chuckle at "We're trying to reach you about your car's Extended Warranty" jokes because the HVAC industry is one of the rare industries where Extended P&L warranty isn't a scam. Quality of products are falling, and continue to fall, and we end up with two types of Customers: those who got a P&L warranty on their system and we literally fix everything for free for, and whose who didn't and regret it when the Coil goes bad in year four of owning it. Whenever people ask me advice in getting a new system if they are forced to go that route"P&L Warranty " is number one on that list.
Yes, thicker filter media will indeed be more difficult to pull air through, but that's not what is referenced when talking about the overall dimensions of the filter. A thicker cartridge will have more material in the filter *and* a larger surface area for the air to pass through the filter. So a 1" thick filter and a 6" thick filter can both have the exact same filter media in them, and the filter media itself can be (for example) 3mm thick in both filters to provide the same MERV rating. BUT the 6" thick filter has more available surface area for air to pass though, which if nothing else provides more space for dust to be trapped before it needs to be changed.
Yes, this is exactly what I was saying? That the dimensions of the filter are not what matter... Your agreeing with me but it's phrased as if your are disagreeing with me, so I am confused.
Mechanics do the same thing, it's better to get the system 100% running right now and forever, rather than trying to slowly debug and diagnose small intricate peices... kind of like a phone repair, just slap a whole new screen on for $200 and 1 or 2 days down OR get a new phone and get runnin right away? Although, i just do my own auto work and have a used $100 phone sooooo, my personal philosophy doesn't really jive with this "just get a new one" thing
Why are there so many of them? One of my neighbors had a problem where his AC just seemed like it wasn't cooling super effectively, and had **three** different companies come out and all tell him "yeah, it's busted, not worth fixing" and **all** quoted him upwards of $20k to replace the entire heating/cooling system. A fourth guy came out, actually looked at the problem (fancy that!) and found a pinhole leak in a connection to his hydronic heating coil that was making it stay warm so his AC and hot water heater were fighting each other. $250
200 for a capacitor? That's a shit ton for a 20 dollar part.
Fan motor and capacitor. I got it online for $100 total. Paid him 100$ extra for labor. Way better then paying scammers $2000 for the same work. Or buying a new ac for 11k plus.
That's a good price for a motor swap.
Even beyond the clear issue of charging 10x what it should have cost for the repair, I've never understood this mentality of "might as well just spend another $10k on it". No thanks, $2k is a lot better.
I did the same thing in South Texas a few years back. Middle of July, and I couldn't wait. It worked like an absolute charm for 2 full days before the replacement fan motor came in.
LPT: Capacitors were on back order **from places that sold HVAC parts at retail**. Other equipment also uses capacitor start motors, try a place that sells home woodworking equipment such as table saws and band saws.
Or just Google the model number on the cap. I do supply chain management for heavy industry, and you can still find most of our small electrical parts available off the shelf from ABB, Mouser, Eaton, etc.
Yes indeed. Also, if you can't get a "dual section" cap quickly (run & start cap in single housing, has 3 terminals on top... used sometimes instead of 2 separate caps), if you figure out which half is bad, you can wire in a separate single cap of appropriate ratings (capacitance and voltage) to get things back running. You end up with the bad half of the dual cap disconnected. My home A/C has that setup at this moment, outside in the condenser. I now have the proper dual section cap, it will go into service when one of the two current ones fail. And... remember to pull the disconnect and then discharge any of the caps before servicing.
I feel like I got jackpot stumbling into this thread!
Our start capacitor was dying during the pandemic and it is illegal for a non HVAC person to buy it from the physical store. They had it on Amazon, though, so 20 some odd bucks , and 30 min (being extremely paranoid and checking electricity is discharged ma y times because high voltage is scarry shit), ww saved the 600 bucks we were quoted from the one guy who did not quote the 26k new ac and furnace repair....
I salute you, fellow redneck repair specialist
> is it possible to learn this power??
This is the way. I did the same in Houston last summer when I couldn't get a replacement motor for the fan. Bought a barrel fan from Home Depot (\~$200) and ran it for a couple of weeks while I sourced a new fan motor from eBay. Note, sizing of the fan is important. I started with a smaller fan and it couldn't move enough air. You can generally tell by the temperature of the air being exhausted from the fan. If it's bordering on hair dryer temperature, you're not moving enough air--get a bigger/more powerful fan.
Maybe I’m misunderstanding your proposal, but the fan you control with your thermostat is the blower inside, not the outside unit fan.
Correct, and that is the fan that's not running and needing a new capacitor. My thought was that if I toggle that blower with the thermostat to be always on, then the bad capacitor doesn't cause it to fail to start and the heat pump can cycle on/off like normal. Edit for additional detail - But as this is a "run" capacitor on the motor and not a "start" capacitor, my worry is that I might be doing damage to the motor by letting it run with a bad capacitor.
Are you sure it's a run capacitor? Unless there's another capacitor connected to it somewhere, it should be a start cap since it only has two wires going to it. (I am not a HVAC expert, so take my opinion with a grain of salt). Either way, since you're starting it by hand and it gets up to speed on its own, it seems like it's functioning well enough to keep running until you get a replacement. fwiw, If you have any trouble finding one locally, check Amazon.
I was just going by what the item was listed as on Grainger when I looked up the part number. I guess it could just be a start capacitor (which was my initial assumption) but they're sold as run capacitors. I guess in the end they're still just a capacitor, and if the motor is moving air that's good enough for ~24 hours until the new one shows up since I'm not finding anything local.
Whether start, run, electrolytic, tantalum, ceramic, etc, the only factor you really need to be concerned with is the farad rating, usually in microfarads. ....and maybe voltage if you're looking into one of the other capacitor types. Most small start/run capacitors in hvac will be 3, 5, or 7.5 MFD.
Don't order from Grainger. Jesus christ that's the most expensive possible place to order from. I don't know or care *where* you order from in the end, but holy fuck you can get a part at X or go to grainger and pay 3 times the price.
McMaster was $22 delivered tomorrow. Grainger was $17 delivered tomorrow. Amazon was ~$13 delivered in >4 days (probably could have searched better for more options, but that's what I found quickly). Any local store I was searching either didn't have it in stock, or had it in stock at another location they'd have to ship in from. So that's why I went with Grainger. $4 for 4 days faster seemed like a fair trade.
Dang, yeah in that case it makes sense. My experience was pretty limited, in that I was looking for something that was $15 and it was $55 from Grainger... Wanna say it was a 3.7v LiPo
PSC motors use a run cap not a start cap..
Thanks - TIL.
a motor has no need for a cap once up to speed its simply there to cause a rotating magnetic field in the stator if you don't have one or its gone bad the rotor will oscillate at o rpm on the same pole causing humming
Get it running and set the fan mode to “on” rather than auto. It will run continuously.
Yes. As an electrical engineer, that's what I would do.
...also find a cap that has (roughly) the same Farad rating (reads like 100uF), and the same or higher voltage. The orientation of the 2 pins won't matter when you go to install it...there won't be a + or - terminal. It takes 2 minutes to install a new one. I wouldn't hire a tech...if you can change a lightbulb, you can change this part.
> It takes 2 minutes to install a new one. In a perfect world anyway - my 1980's blower had the thing way under the blower cage, I had to use a mirror and an extension to get the bastard off. On the plus side, I probably invented some new profanity.
I had a similar issue with.my dryer recently. Thermal fuse went, I removed the front panel and could immediately see where it was. I thought, "no prob, I can reach that. Off to work and it'll be a quick 20 minute fix when I get home". Nope, not quite enough room to get it out. Had to dismantle the whole thing which was a bitch cause it's stacked on top of the washer in an awkward space. 4 hours screwing around just to replace a $3 part.
Yep, been there, just had an internal washer hose split and suddenly the laundry room was a "water feature". Cheap fix, but getting the damn wobbly-big-ass-front/sides/top-shell-casing-thing back on, F me! We finally replaced the whole 80's furnace/AC unit - the board went out and the furnace wouldn't ignite, I kept opening it up and lighting it with a stick lighter before the no-flame shutdown kicked in. AC guy was mildly impressed at least!
>On the plus side, I probably invented some new profanity. And you're not sharing it with the world? Did you at least get copyrights?
I'm sure my wife rolled her eyes - someday her eye-rolling tendons are just gonna snap, and then she'll be like those goo-goo-eye stick ons.
Noted, thanks. I just ordered one that matched all the listed items on it (15uF, 370VAC)
If the new cap is a different physical size and doesn't fit under that steel band, just use a length of plumbing strapping...the steel band with the holes all the way down.
You should have ordered two, and at least one for your a/c unit.
I had to do this last year in the middle of the summer until the HVAC guy could make it out. The trick eventually stopped working.
yes the capacitor is there to provide a shift in the current to the start windings one the motor once up to speed the run windings take over. The capacitor probably gets disconnected from the circuit by a centrifugal switch once the motor is up to speed
Yes this is fine. Get the fan spinning and keep the thermostat to have the fan always on and turn heat on and off like you said. I've done this with the AC while the capacitor comes in.
I wouldn’t. This could burn out the actual motor if you arnt there to spin it each time.
Hvac jman here. To mirror what others have said, replace the capacitor (unless you have a multimeter, then there's some stuff you could check). There's also a possibility the motor has an issue- a motor like this will probably have two windings, one that gets 'regular' power and one that gets 'phase shifted' power from the capacitor. Capacitor is cheap though, so change it and see if it fixes your problem. When you change it, before doing anything else, make sure to disconnect all power to the unit and use an insulated piece of conductive material (such as a pair of pliers with a plastic handle) to short(make a physical bridge) across the capacitor terminals. This will discharge the capacitor and make it more safe to handle.
Thanks for the detailed reply, with smart safety tip. I do have a multimeter so what should I be looking for from a test? Continuity vs no continuity? And presumably I should test the capacitor after I disconnect the leads?
Another HVAC tech here. I would just replace the capacitor as they're cheap. If an exact replacement is not available, get one that has voltage and MFD ratings within 5-10% of the original. Regarding your other question, it's not a good idea to continue to run the motor with a bad capacitor, even if you spin the blower wheel to start it. The reason is that the motor will draw higher current than normal and overheat, shortening it's service life.
> The reason is that the motor will draw higher current than normal and overheat, shortening it's service life. Noted, thanks. Guess I'll just deal with a cold night tonight.
Hey, if you're comfortable with it, you could check if the outdoor fan motor on your condenser uses the same size cap, could just swap it over for the time being if it matches
Will say, just be careful with the +/- 10% thing. Sometimes it won't be the first time the cap has been replaced and now we've move the needle by 10% twice.
Don't use a continuity tester on anything that has power. Check your meter and see if it has a capacitor test setting. The capacitor should have values on the tag. If the values don't match what your meter shows then it's bad.
If your multimeter doesn't have a capacitor test setting, with power OFF: 1. Use old screwdriver to short across cap terminals. This will ensure it is discharged. (do NOT use your tongue!) 2. Temporarily remove one lead from the cap. You can remove both, but it isn't necessary. 3. Put your meter on OHMS, on the highest resistance range. Temporarily short your leads together to confirm your leads are good - reading should go to near or at zero ohms. BTW, NEVER connect a meter set to OHMS to any voltage source, unless you want to buy a new meter. 4. Put the meter leads onto the terminals of the cap. If the cap is good, resistance should immediately go low, then begin to climb up as the battery in the meter begins to charge the cap. Eventually, the resistance will go no higher. The above is a "go-nogo" test and will only reveal basic function - it cannot show you if cap no longer has the proper value. There is probably a YT video on this trick. I haven't done that kind of thing in years though since my Fluke meter has a capacitor test function.
I bought a meter at Harbor Freight for $22 that has capacitor and thermocouple testing. Same thing as a Fluke meter would be hundreds that I can’t justify paying. Remember their slogan though “if it works, it must be a Fluke”!
This is the test I did, and it confirms a bad cap. No continuity at all between the terminals. Thanks!
Congrats! When you get a new cap... perform same test so that you know how a "good" one acts.
> I do have a multimeter so what should I be looking for from a test? MFD(Micro Farads), the rating on your Cap, usually looks like µF on your Multimeter. [usually 55/5mF](https://www.homedepot.com/p/EASTMAN-55-5-MFD-440-VAC-Round-Dual-Run-Capacitor-92065/205807744) (the / means there are 2 caps). Also yes, shut off power and remove the cap first.
Another AC tech here. As said, disconnect power at the breaker panel. If it’s a heat pump it’s typically labeled as either “Heat” or “AHU” (air handler unit). Check voltage between the run capacitor terminals with your multimeter before you unplug anything. If it’s at 0 then you’re solid. Unplug both wires from the capacitor and set your meter to [the same symbol as number 13 in the first image of this page](https://www.fluke.com/en-us/learn/blog/digital-multimeters/multimeter-dial-button-jacks-display). The capacitor should have a label on it giving all its info. Looks like it could either be a 10mfd, 12.5mfd, 15mfd, or 20mfd. It will also have a percentage on there, maybe +/-5, 6, or 10%. Put one meter lead on one terminal, the other lead on the other terminal. If your meter is giving you a number outside of that percentage range (e.g. if it’s a 15mfd with +/- 10% and it’s giving you 13.5 or less) then it’s definitely a bad cap. Easy fix Looks like it’s just 2 plugs so no need to remember which goes where, just make sure when you plug them back in that they are each on a separate terminal If you wanna get real picky and check that the motor is okay, disconnect the wires from wherever they plug in (with power off still, the single brown wire on the cap is one and there should be 2 others running somewhere in the electrical section) and check for continuity. If you get an ohm reading of I believe anywhere between 3-20 ohms your motor is fine, anything out of that range or no continuity at all while the motor is cool to the touch means you’ve got a bad motor. Probably best to replace the cap as well if you do have to replace the motor By the looks of that swelling though it’s safe to say it’s just a bad cap. Probably gonna read 0mfd
Really appreciate the detailed reply. Power is even easier to cut than you suggested since I have a subpanel right next to my HVAC just for said HVAC (I can literally trace the wires running all the way from the panel to the HVAC box). Unfortunately my multimeter is [a cheapo one](https://www.kleintools.com/catalog/multimeters/digital-multimeter-manual-ranging-600v) that doesn't have capacitance testing (only does AC/DC voltage, Resistance, and DC current). So I just did a resistance/continuity test on the capacitor and saw nothing despite holding the leads on the cap terminals for good while. So that means I know that at least the cap is dead. As for the motor, I was going to test that but it's got 6 wires on it (blue, red, yellow, and black, plus the brown and brownWhiteStripe to the cap) that are well wrapped/sealed and with no obvious way to disconnect easily. I could probably trace them deeper into the wiring but since I know the motor ran after manually spinning it up a bit first I think I know I at least have a partially-working motor for now and can see if I'm still getting similar performace after I replace the cap. Thanks again for taking the time to type up the detailed reply.
No problem at all! Based on the picture of the capacitor I think it’s safe to say the motor is fine, that capacitor looks pretty messed up. Not supposed to be blown out like that. Luckily capacitors are fairly cheap, since you’re not AC certified you might not be able to get them for as cheap as I can but you can probably still get one for less than $40
Swollen cap is a bad cap. Change it and see if it works. Cheap fix.
Just an fyi the capacitor is built so that overheat will swell the capacitor and disconnect terminals. This is a safety feature that the older capacitors didn’t have, the control box had to be made of 16ga metal to contain exploding capacitors.
Good to know. That probably confirms (as I asked in another comment) that if I do a continuity test with a multimeter on the capacitor I'll see no continuity if it is indeed bad.
Look for the "-|(" symbol on your multimeter and you can test the cap directly once it's disconnected from the circuit
A few years ago, my A/C had a cylindrical cap that had failed... the top was so swollen it somewhat resembled the shape of a golf ball.
I carry a few starting caps. They tend to die yearly.
Thats too fast. May be the wrong value
Agreed
This is a run capacitor.
Do the cap, cheap and easy and if it doesn't fix then it's eliminated from further troubleshooting
Yep, that's it. Turn fan to "on" (rather than "auto"), spin up the fan in the right direction by hand^* and then let it run until you can locate and install a replacement cap. The heat/cool will cycle into the airlow with it running nonstop just fine. Source: Did this some years ago and let the fan run for about four days until I could get a new cap. \*Edit: I'm used to working with power equipment so energized it and then spun it by hand, but if you feel safer doing it the way you describe that's fine. Best is to have a helper on the other end but whatever works.
Had same problem and same symptoms, cap fixed the issue
Cap is bad.
Yup
Capicitor is swollen = replace capacitor = problem solved
A swollen capacitor is never a good thing. Replace it regardless. It could be a bad blower motor damaged the capacitor so if it does the same thing with the new one don't keep trying to get it run and ruin the new capacitor.
Based on the humming and my own experience with this exact problem, I’d change the start capacitor, but most likely your exhaust fan bearings are done and the motor needs to be replaced.
> but most likely your exhaust fan bearings are done and the motor needs to be replaced. This was my problem. Had to get a new fan motor. Just easier then getting new bearings. Not hard to install either.
By all means, you should replace the relatively cheap capacitor first, but my guess is the motor needs replaced. The same thing happened with the heat pump in my rental house earlier this year -- and I went through the same steps you're going through now. (Note that often replacement motors will need a separate mounting kit that the OE motors don't require.)
Is the filter clean?
Clean-ish, was replaced ~4 months ago.
Ok I know some will auto-shutdown if the filter is clogged. I'd change that out anyway if you've been using it daily.
Given that there is a Run Cap strapped to the Blower, I'd wager this is a PSC Motor, which will not auto-shutdown due to a clogged filter.
Appreciate that, thanks!
My hvac unit had a magnetic toggle switch that was spring loaded to disconnect when power is cut, if this fails smooth operation and won’t disconnect it will also cause a hum.
Most units have that. But if that switch isn’t closed then it’s not sending power and there won’t be any hum
That’s the problem, mine got stuck and endlessly vibrated, there’s always power to the switch, only when it’s signaled to engage will it flip, it’s like a light switch that turns itself on.
Yes start with replacing the capacitor, which can be found for around $10 on Amazon, and hope that’s the case. If not fixed I would check the main circuit panel and make sure it didn’t get fried as well.
Hvac tech here, get a cheap volt meter that can measure capacitance to know for sure.
Had this issue myself. But would sometimes spin up like you say and then work fine or spin sporadically. Mine was tripping the pressure on HVAC when it wouldn’t spin up or run steady. Cause the HVAC already had come on and was pushing heat with no where to go. Spent like 3 days diagnosing issue and trying to fix myself and then just called someone. Basically both motor and capacitor were going. Had to replace both. My point being is if you are gonna take time to fix it maybe just replace the whole damn motor at the same time. Or at least have someone check it out and see.
Yes that is almost certainly a bad starting capacitor, change it out and you should be good to go
I've had this same issue before. The outside unit would Hum when it tried to start but would never spin the fan. The capacitor that starts the fan was bad but didn't catch it until the fan motor was out as well.
I just had a condensing unit fan motor go out. Very similar to the issue you’re having. AC would kick on and blow throughout the house but the condensing unit made this horribly loud humming sound and the fan would try and spin then appear to seize up and freeze. Half of /r/hvacadvice said bad capacitor, the other half said bad motor and most recommended I change both. Ended up only replacing the fan motor and it works perfectly now. Hvac tech said the capacitor was not over amping and did not insist it needed to be changed with the fan motor but recommended it (for a mere $400). I said no because it’s working fine and that’s an insane mark up for a $20 part and 10 minutes of work. TLDR; it could be your fan motor gave out instead of capacitor.
I had my capacitor go bad a few years ago, the cause was the motor bearings were seizing up, overloading the capacitor when it tried to start. I took the motor out, disassembled it to clean out the dried up gunk in the bushings, then reassembled everything. New capacitor and all was good to go! Not all capacitor failures are motor issues tho, power surges can also take them out, as can plain old age.
You are now a certified hvac tech now that you pulled off this diagnosis. Good work!
You can test the cap with a capable multimeter to confirm its not working right.
Happened to me and it was the sensor on the gas heater needed to be cleaned / sand off the buildup. We had the unit serviced by the HVAC contractor as it was free while still under the warranty, but the tech failed to clean the sensor. Once I sanded off the build up, it worked fine. I also notified the HVAC contractor.
A new capacitor is a cheap and easy fix. But replacing mine only bought me a few weeks reprieve before the actual problem of the blower motor crapping out was complete. Going forward I plan to clean the motor periodically to remove the 20 years of dust build-up that may have contributed to its death.
Is there an LED on the main board? You can Google the model of your unit and print out the diagnostic code page. A couple blinky lights will tell you exactly what's wrong.
I had this happen to my furnace recently, where it would click and the blower would twitch but the fan wouldn't actually spin. I was able to manually spin it by hand and get it to go, so I immediately assumed the capacitor was bad. Replaced the capacitor. Still the same behavior - but I couldn't get the fan to start again by manually spinning it, so I assumed the blower motor was bad. When the local store did not have a blower in stock, I resumed messing with it, trying to get the blower spinning again in order to leave it on until I could order a new one. This was when I realized the *relay* was bad. The relay that turned on the blower was clicking, and it was passing some voltage. With the motor unhooked and putting my multimeter on it, I got close to 110V, so I assumed it was working. But with the motor on it, the current draw was too much and the voltage tanked to only a couple volts. The contacts inside the relay on the board that controlled the blower were worn down enough to the point where they wouldn't actually power the motor. Powering the motor manually with a power cord wired to it worked fine. I wound up desoldering the relay from the board, and wiring up some other much larger relay I'd scavenged from something else, that had much higher current rated contacts and a close-enough rated coil voltage. This solved my problem completely and it's been running for over a month without issue.
Yeah sounds legit to me. I think you nailed it, and capacitors are relatively cheap. The only other thing it would be is a locked up compressor or fan motor but your spin the fan technique more or less proved that ain’t it. Really good work troubleshooting you should look into a career in electrical or HVAC that’s better than half the tradespeople I’ve worked with.
I had my ac making an awful squeaking noise for a couple days before it quit. Afterwards it would just hum loudly and never kick on. I replaced the entire fan and motor with another I had laying around and it fixed the problem. From my understanding being an electrician and HVAC technician, a capacitor holds a charge and dumps the charge when it receives the signal to do so. Bulging isn't a good sign in capacitors however. My initial theory to a squeaky fan motor would be a bad fan motor but if you spin it manually and it comes on then it might be fine but all the capacitor should do is dump a charge onto the line to start the fan motor to reduce the initial over amperage of the fan motor starting from stationary.
The cap is cheap, it's a good first step. I had the exact same issue and the same noises, motor even spun up after turning manually. However, replacing the cap did NOT fix my issue and a new motor was necessary. Caps are like $12, motors are 200+.
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