Furnace Turns on when not supposed to - Help Please

[mtor9477]

Hi guys,

I have a Coleman Evcon Gas Furnace, Model #DGAT056BDD (1997, Heat Only).

For some reason, after heat reached right temp, it turned on again (when temp was at or higher then set at t-stat) and was blowing non-heated air. I tried turning the t-stat down and even off and the furnace kept blowing. Only way to shut it down was at the breaker.

I also checked the codes the first time it happened and it blinked 6 times that translated to "Wrong voltage or polarity or something wired to furnace"...which makes no sense since the furnace operated correctly since 1997 (except for circuit board change one time due to moisture).

The only difference was that I replaced the mercury t-stat with a digital one over a year ago. Haven't done any additional troubleshooting except for what's noted above.

One more thing...this is a secondary home and when I arrived late last Dec, I noticed the furnace was not running when temp dropped and I heard some kind of quick 'buzzing/clicking' sound. I shut the t-stat to the off position and then to on and it started working again.

I think it's the circuit board. Any suggestions?

Thanks in advance!

~Mark

[Robert]

Replied to email.


Thanks,
Robert