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.
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.
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