[joshuaaap]

I have a Lennox 80UHG furnace that quit working yesterday. I can turn the blower fan on by switching the fan from "auto" to "on" but the heat will not kick on when the thermostat is set to "heat." I have the temperature set above ambiant room temperature but nothing happens. There are 2 green diagnostic lights that flash slowly together supposedly indicating normal operation. Normally, the combustion air inducer will kick on, the gas will be ignited by an automatic igniter and then the main fan will kick on after a little bit. There's no clicking or fans coming on and all I can hear is a very faint humming sound. Can anyone help me diagnose the problem.

 

[joshuaaap]

Update: I tried "jumping" the furnace by running a wire from the W to the R terminals and the furnace starts up and runs just fine. Could there be a problem with the thermostat? the control board?

 

[danpik]

Pull the thermostat from the wall and jump the same two wires again at the stat connection. If the unit fires then the stat is bad. That stat doesn't have batteries by chance does it?

 

[joshuaaap]

Yes, the thermostat has batteries. I changed them out but it still wasn't working. I had an old stat that I installed late last night in case the digital stat was bad and the furnace fired right up. I wish I would have posted here sooner and saved myself a lot of time fiddling with the furnace. Thanks for the advice anyway though.

 

[jagans]

Damn nice call DanPik ! :thumbsup::thumbsup::thumbsup: What do you mean thanks anyway? The Guy nailed it pure and simple. Where I come from Thanks Anyway means nice try, but I got it myself.