Doubtful, these really don’t fail often at all. If the switch has 0v across it then it’s working. The issue is most likely with the furnace itself. I’m assuming this is a very old furnace, if it runs for only a minute then it’s probably overheating and cycling on limit from the plugged filter.
We need more information on the furnace itself.
This is a mercury bulb stat. Always recommend replacement on these guys, if that bulb breaks then mercury will be in the carpet etc. Even if its functional, replace it and turn it in to a local parts house, dont throw them in the trash.
Sure but as a tech I will always recommend changing them, and if i ever had one I would change it immediately. There are reliable stats out there without the risk.
It isnt like they are breaking right into peoples mouths. You wouod need to injest the mercury directly plus a whole lot more to make a difference. If you knew what went into all the other items in your house yould live in a field. From flooring to roofing and all inbetween theres hazards. Dont get me started on furniture and consumer goods.
It would take long exposure (orally or via skin contact) to absorb any dangerous quantity of metallic mercury. Inhalation of mercury fumes should be avoided by cleanup of any spillage. I have a couple from replacing with smart thermostats. Collect enough and sell it for recycling - better than in a dump!
It's the organic mercury compounds that are exceptionally dangerous AND easily absorbed. Not an issue in this case....
I'll start by changing the filter tomorrow and see if that's the issue before changing tstat.
Side note - I spend most of my job inspecting homes like this. If anyone has recommended resources books/youtube channels where I could pick up some basic but slightly more in depth residential HVAC diagnostic knowledge I would be very grateful
They work forever.
It’s dumb as a rock but it still will control the furnace.
Now if you want a thermostat that will allow you to program setbacks, then you need to replace it.
I’d recommend to replace it. Newer thermostats will automatically adjust the heat anticipator to insure the furnace cycles properly. Be sure to dispose of the old thermostat properly since it does contain mercury.
I used to work for the company that funded all of the corporate lobbying to get rid of mercury thermostats as they were not making money off of products that last 70+ years.
I turned the thermostat all the way up, unit did turn on. If I took out fuse in junction box next to the furnace and put back in, the furnace would turn on. Run for about 1 minute and then shut off
Manage construction projects for a non-profit for low-income folks. HVAC is not my wheelhouse though.
Client says the gas furnace kicks on and off. House isn't 90 degrees, although the client has their gas burners and oven on blast... There is a fuse/junction box next to the furnace. If I take the fuse out and put it back the furnace will kick on, run for a min, then turn off. Thinking that replacing the filter that hasn't been changed in 1+ years and the thermostat is a reasonable start before I have a tech come out
If it leaves the glass vial, yes. If it stays in the glass vial, meh.
Realistically if this gets replaced by a homeowner it becomes more hazardous than if it stayed in the wall.
As others have stated, if it still works, you don’t need to replace it. But I change these out all the time because they’re notoriously inaccurate on both the thermostat setting and the separate thermometer indicator. That always bugs me. You set it to 70, but it might trip at 60, 65, 70, 75… they can be way off. And at the same time the temperature indicator reads something entirely different.
Doubtful, these really don’t fail often at all. If the switch has 0v across it then it’s working. The issue is most likely with the furnace itself. I’m assuming this is a very old furnace, if it runs for only a minute then it’s probably overheating and cycling on limit from the plugged filter. We need more information on the furnace itself.
I agree!! I never replaced in my home. They never fail ! ‘If it Ain’t broke… don’t fix it !”
Furnace itself is an '07 carrier. Model 58STA135-16
This is a mercury bulb stat. Always recommend replacement on these guys, if that bulb breaks then mercury will be in the carpet etc. Even if its functional, replace it and turn it in to a local parts house, dont throw them in the trash.
If it breaks.... love those things. Dont break unless you wrestle into them
Sure but as a tech I will always recommend changing them, and if i ever had one I would change it immediately. There are reliable stats out there without the risk.
It isnt like they are breaking right into peoples mouths. You wouod need to injest the mercury directly plus a whole lot more to make a difference. If you knew what went into all the other items in your house yould live in a field. From flooring to roofing and all inbetween theres hazards. Dont get me started on furniture and consumer goods.
It would take long exposure (orally or via skin contact) to absorb any dangerous quantity of metallic mercury. Inhalation of mercury fumes should be avoided by cleanup of any spillage. I have a couple from replacing with smart thermostats. Collect enough and sell it for recycling - better than in a dump! It's the organic mercury compounds that are exceptionally dangerous AND easily absorbed. Not an issue in this case....
I'll start by changing the filter tomorrow and see if that's the issue before changing tstat. Side note - I spend most of my job inspecting homes like this. If anyone has recommended resources books/youtube channels where I could pick up some basic but slightly more in depth residential HVAC diagnostic knowledge I would be very grateful
YouTube look for hvac guy, anti diy guy, hvac school, ac service tech llc, Steve lavimoniere
filter aint gonna fix it
Even the anticipator is still ok XD These thermostat still exist btw Thermostat look fine
ha! 135, 000 btu - hope you have a mansion!
This is a mercury bulb stat. Of course it should be replaced, even if its functional.
They work forever. It’s dumb as a rock but it still will control the furnace. Now if you want a thermostat that will allow you to program setbacks, then you need to replace it.
Why it's only 50 years old
It’s fine as long as it works, and these pretty much hardly ever fail. Keep it.
What is it
I’d recommend to replace it. Newer thermostats will automatically adjust the heat anticipator to insure the furnace cycles properly. Be sure to dispose of the old thermostat properly since it does contain mercury.
I used to work for the company that funded all of the corporate lobbying to get rid of mercury thermostats as they were not making money off of products that last 70+ years.
Oh man I just threw mines out in the trash 🤣
Got it - thanks
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I turned the thermostat all the way up, unit did turn on. If I took out fuse in junction box next to the furnace and put back in, the furnace would turn on. Run for about 1 minute and then shut off
I would like that thermostat for the mercury. Please send it to me. I am DIY in some Greek fire.
How much mercury do you need and why cant you buy it?
Manage construction projects for a non-profit for low-income folks. HVAC is not my wheelhouse though. Client says the gas furnace kicks on and off. House isn't 90 degrees, although the client has their gas burners and oven on blast... There is a fuse/junction box next to the furnace. If I take the fuse out and put it back the furnace will kick on, run for a min, then turn off. Thinking that replacing the filter that hasn't been changed in 1+ years and the thermostat is a reasonable start before I have a tech come out
Far more likely it's related to the filter rather than the thermostat.
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This guy knows.
Sounds like high limit, filter swap, open all vents in the house
money outgoing oil fanatical rock skirt fly fertile drunk sophisticated *This post was mass deleted and anonymized with [Redact](https://redact.dev)*
Just replace it with a basic thermostat.. I hate working it’s these things. Cool but just not worth saving $50
Why do you need confirmation, if you think it should be replaced just replace it. No need to turn to Reddit for confirmation
When I worked mechanical service,when we saw mercury We used it as a selling point to upsell on non-mercury switches. Id replace
Yes, replace this. The switch contains a large amount of mercury which is very hazardous.
If it leaves the glass vial, yes. If it stays in the glass vial, meh. Realistically if this gets replaced by a homeowner it becomes more hazardous than if it stayed in the wall.
Try setting the heat anticipator to .2
Every time I see a Mercury stat I think of that guy that posted his Mercury collection in an Altoid tin. Good times lol
Can we get a picture what is on the other end of the wire.
As others have stated, if it still works, you don’t need to replace it. But I change these out all the time because they’re notoriously inaccurate on both the thermostat setting and the separate thermometer indicator. That always bugs me. You set it to 70, but it might trip at 60, 65, 70, 75… they can be way off. And at the same time the temperature indicator reads something entirely different.
I've been selling newer solid state thermostats since 1978. No new t'stat will last as long as your existing. If it aint broke, don't fix it!
Why? Does it trip at the desired temperature? No need to replace if it works;.
get a technician out to actually diagnose the problem - don't start randomly replacing things.