Thermostat issues

Question

Due to a wiring issue (my fault) I recently replaced my thermostat with a Coleman 6636-3441 Digital Wall Thermostat. We encountered unusually cold weather for eastern Ariz., night time temps in the 20's and 2" of snow one night. I have never needed my heater before but have tested it to make sure it worked, (sort of). Problems were that I would set the temp before we went to bed and the heater would kick on once but not again as the temp dropped. If I turned the switch to off and back to heat it generally worked again. Second problem was sometimes the pilot would light but when the gas kicked on it would make a blow out sound and the fan would shut down because the gas "flame on". I guess these could be two unrelated issues but I would appreciate any ideas.

old-biscuit · Answer

Which furnace do you have........pilot flame???
Most don't have a pilot flame any more unless you have an older model.

Does A/C Unit work correctly?

How did you wire it?

That thermostat is for use with gas furnace and two stage a/c

sjturbo · Answer

Thanks for the reply OB! It's a 2010 Larado so my inference to a pilot is likely incorrect. The 5'r is three hours away so I cannot tell you the mfg at this time. The A/C does work correctly as far cooling but I did not check to see if it works in auto at different temps. The wiring was just a plug in replacement for the older unit so I made no changes.

old-biscuit · Answer

Plug and play so issue is most likely at furnace

BUT not knowing what it is doing and what it doesn't do makes it a guessing game.

Does it reach temp set point before turning off?
Does it attempt to run when temps drop......fan start, hear click of spark, main flame light at all?
Any lights on circuit board? Flashing green red number of blinks etc. are error codes.

Could be mis-positioned spark electrode, low battery voltage, dirty sail switch, bad circuit board, bad gas valve etc.

WHY did you change out thermostat?
Was furnace working correctly prior.....or had issues?

sjturbo · Answer

Thanks OB. Actually the first time I had to use the furnace in such conditions.
Reaches temp before turning off - Yes
Seems to attempt to start when temp drops (sometimes).
I am actually storing the unit at a remote location so I believe I will need to continue this thread when I have the unit in hand.

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Thermostat issues

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