I have a comfortmaker furnace(model# GUG141A020IN) I have been working on this thing for 2 Days. Came home house cold, when I turn up thermostat "nothing", jumped it at furnace and it cycles up as normal. Now get this, if I turn up the temp and flip the switch from heat to OFF and flip it back to HEAT the thing fires up (sometimes) and runs as normal until it reaches the set temp, once it reaches the set temp it cycles off as normal. BUT when the temp drops below the hold temp, the thermostat calls for heat but the furnace does out respond until I go back through the afortmentioned routine. I've changed the control board and thermostat and still have the same problem. Furnace supply guy thinks it may be the relay(does anyone agree). I got a strong feeling that it is something simple that's KICKING MY BUTT... HELP and yes I know for the money I've spent I could've has it serviced.

You are resetting the control board fault any time you remove 24v from the W circuit. Its what we call a soft reset, its not a major fault but a fault that needs to be addressed. If you will count the blinks of the lights on the control board before you remove 24v or 115v it will give you the code to the fault.

Quote: ( jumped it at furnace and it cycles up as normal. ),, jumpered it, what is it? Are you saying you jumpered tstat wires meaning bypassed the tstat?, if this is the case you also bypassed the tstat wires running from furnace to tstat, if this not the case, what did you jumpered?

OK T-Top I'm quite the newby at this... what do you mean by remove 24v from the W circuit? I get that I need to count the blinks of the light on the control board but you lost me with "before you remove 24v or 115v". The lights seem to continuously flash to me during the cycle through. When should I be counting the blinks. And again please forgive me if I sound like a complete idiot lol.

Yes I bypassed the tstat... "jumped" the R and W where they connect to furnace... and the furnace cycled through the start process as if It was starting normally from the tstat.

Any time you remove a thermostat or turn it off and then back on you reset the control board if it's a minor fault( by removing 24 volts from the heat call). You have to remove 115 volts from the system and then back on to reset a major fault.

I have an older model furnace with an external low voltage damper above the furnace on the exhaust, apparently the damper was not communicating properly with the furnace. The damper has been set to always stay open and now the furnace seems to be working as advertised. If it starts back giving me problems I'll disconnect it from the furnace... I would have did it already but didn't want to take a chance of screwing something else up.

To be honest I don't know why you would have a vent damper on your 80% furnace any way.

It was there when I brought the house!! Frankly didn't even know what the H*ll it was... live and learn