What's this furnace part called?

Dave Sherburne, NY · Jan 22, 2015

A friend of mine gave me a small gas furnace when he got a bigger one. He told me this part was bad. It's supposed to turn the blower fan on when the furnace heats up and off when it cools off and the thermostat is calling for heat. I checked it and it closed the circuit when I put it in front of an electric heater but would not open the circuit when it cooled off and if the fan doesn't stop, the furnace won't start up again. what's it called and where can I get one?

pat sublett · Jan 22, 2015

If it does what you described, it is a blower control thermostat. Google appliance parts.

rrc300 u · Jan 22, 2015

It's a fan switch. it probably just wore out. them little bimetal discs only have so many snaps in em

Bruce SEKs · Jan 22, 2015

High temp switch, ohm it out, no big deal, furnace will run for a while then shut off, after it cools down it will start up again

old1850d · Jan 22, 2015

I agree with Bruce , its a high temp limit , just look for some markings on it , most of them will be in the 170 degree range , but differnt for each brand, not very spendy

MartyinVa · Jan 22, 2015

Young son that is in training says it is a high limit (temp) switch.

CJinMI · Jan 22, 2015

Fan OR limit. What's it say on it, a letter then numbers,L =limit, F=fan, then the degree it operates at. You say its fan, but the fan stuck on "the furnace won't start up again" tells me Limit. The blower stuck on should not affect furnace on and off. Limit stuck usually- depends on the control-does what you describe. And to the other poster "no big deal" it is. If it trips there is something wrong, and many times they WON'T reset. Furnaces, among many things posted about, are something a person shouldn't be to cavalier about. Controls and safety circuits are there for a reason. Google furnace parts, plenum thermostat, fan switch, limit switch, lots of places to get them (I don't know what you have local).

Steve@Advance · Jan 22, 2015

Is the furnace connected to power? If so, temporarily connect together the 2 leads that plug on the switch.

If the connection controls the fan, it's a fan cycling switch. It's purpose is to delay the fan until the heat exchanger is hot, that way the furnace doesn't blow cold air when it first calls for heat.

If the connection controls the gas valve, it's a high limit switch. Very important! This protects the furnace from overheating if the fan fails to run. Not an area to shortcut! Fire hazard!

If there is an HVAC supply house near you, and they will sell to the public, they should have it. Or go online, search for HVAC parts. You'll need the make, model and serial #s.

Bob · Jan 23, 2015

There's a schematic diagram on the furnace that will show you how it fits into the circuit.

And, likely, there's a number printed or stamped on the thermostat that when GOOGLED will return results as to what exactly it is and sources and $$ of a replacement

ShakerPrairie · Jan 23, 2015

Dave lookup a place called partsguy.com
I've bought fan switches ect from them online.

What's this furnace part called?

Dave Sherburne, NY

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pat sublett

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rrc300 u

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Bruce SEKs

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old1850d

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MartyinVa

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CJinMI

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Steve@Advance

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Bob

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ShakerPrairie

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