||01-26-2013 09:47 AM
Need help with Lennox G40UH furnace
Hi all - I have a Lennox G40UH-series gas furnace that is behaving erratically. I have it connected to a programmable Honeywell thermostat that calls for heat in the morning and AC during the day (in Florida). One morning last week the heat didn't come on: no burners, no blower, LEDs on circuit board both out. When I got home from work, the AC was running fine. Next morning, the blower came on but was blowing cold air; the furnace was not lit. The unit wouldn't shut off from thermostat, so I did a hard reset from the breaker box. Still no lights on board. I checked voltages on both sides of the transformer and at the thermostat; all good. Later that day, both the AC and heat fired up no problem. Next morning, same deal, nothing was working again. I thought it might be the ignition board, but I decided to have a tech come out yesterday. He replaced a bad float switch and the run capacitor on the blower motor and had the AC running fine with both lights green on the circuit board. I thought we were good. This morning, however, back to the same: no lights, no blower. Already checked the thermostat. Any ideas?