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jaycafe
10-04-2010, 07:09 AM
I have an issue with my furnace not turning off. It will start fine, at the desired temp, but the blower won't stop (only sometimes it stops). I usually have to go downstairs and turn off the power to the furnace for 10 minutes, then the blower seams to reset itself. I do have an electronic thermostat thats only 2 years old and has fresh batteries.
Is there a relay or somthing, that is screwing things up?
Any help would be great!

Thatguy
10-04-2010, 08:25 AM
I have an issue with my furnace not turning off. It will start fine, at the desired temp, but the blower won't stop (only sometimes it stops). I usually have to go downstairs and turn off the power to the furnace for 10 minutes, then the blower seams to reset itself. I do have an electronic thermostat thats only 2 years old and has fresh batteries.
Is there a relay or somthing, that is screwing things up?
Any help would be great!
Please post a schematic.
For intermittent problems I'd check for loose connections.
You can also check for Technical Service Bulletins that the manufacturer may have issued regarding this problem.
Do you have a multimeter?

Dana
10-04-2010, 09:05 AM
Many hot air furnaces control the air-handler with a snap-disc type thermostat on/near the heat exchanger, which should be turning off the contactor/relay for the blower motor once it has cooled. They sometimes get sticky and need replacement. A weak contactor spring or sticky contacts could also have this symptom if the current for the blower motor provides sufficient make-force once it's on that the spring can't break the contact, in which case turning off the power would sometimes be necessary to get it to release.