LikeABigFriedEgg
Member
I have an intermittent problem that my furnace fan sometimes runs when it shouldn't, and the only way to stop it is to shut off power to the whole system, thermostat and everything. It's happened a few times over maybe a couple years, I think. Last time was a couple days ago when it was stuck on for about a day or more, and I had to turn off the whole system except when I wanted to run the fan to circulate air through the house. I don't use the A/C much, but I often use the fan at the same time as a dehumidifier, and then I control the fan manually from the thermostat, and that usually works fine.
When the fan is stuck on and I try to turn it off and on from the tstat, I can hear a distant sound that I suppose is the fan relay operating as it should downstairs, but the fan just keeps running.
Fan operation is usually fine with the furnace in Winter. I think it sometimes stays on for kind of a long time after the burner shuts down though. Maybe five years ago I did mess with the "OFF TEMP." setting on the blower-control module, but probably shouldn't have.
Photos and schematic attached. Please advise.
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Lennox G8Q2-110M, 1968
Carrier TSTATCPPS701 programmable thermostat
When the fan is stuck on and I try to turn it off and on from the tstat, I can hear a distant sound that I suppose is the fan relay operating as it should downstairs, but the fan just keeps running.
Fan operation is usually fine with the furnace in Winter. I think it sometimes stays on for kind of a long time after the burner shuts down though. Maybe five years ago I did mess with the "OFF TEMP." setting on the blower-control module, but probably shouldn't have.
Photos and schematic attached. Please advise.
___________________
Lennox G8Q2-110M, 1968
Carrier TSTATCPPS701 programmable thermostat
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