Faulty Thermostat??

Old 12-27-11, 07:28 AM
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Faulty Thermostat??

This morning upon climbing out of bed , I noticed the house was cold. I checked the digital programmable thermostat and found it calling for heat,but the furnace wasnt running and the house temp was at 60deg.
I switched the thermostat to fan and the fan kicked on. When I put the thermostat back to heat mode it kicked on,and started working fine.
I went to furnace and cleaned the flame sensor as I have had a problem with that in the past not sensing the flame.
The furnace is now working OK and reaching temp and shutting down normally.
Any clue as to what might have happened?
Does this sound like a thermostat problem or possibly the board in the furnace starting to act up.
Old 12-27-11, 08:29 AM
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Could have been a little "film" on the heat/cool switch or the flame sensor getting a little "iffy" before you cleaned it.

Moving the control switches on the thermo should clean the contacts a bit, but since it's now working, I would just keep an eye on it. No need for panic mode unless it quits and you cannot get it to fire up. The control board is usually either good or bad - no middle ground.
Old 12-27-11, 08:36 AM
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Intermittent problems are the bane of repairman.

What I'd do is to take the cover off the burner and carefully observe the sequence of ignition while someone turns the furnace on at the thermostat 20-30 times to see if you can get it to fail.

If it does, see how far in the ignition sequence it gets.

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