Atimu
New Member
Hi, I have a 10 year old Lennox furnace that stopped working overnight. Tried swapping thermostat with an identical functional one, nothing. Green led on board does not light up at all. It is getting 109 volts at the control board but the moment you plug in the 24v transformer, it drops to 0.1 volts at the board where the primary transformer wires connect, and at the other end of the transformer it's 0.02, so transformer's stepping down what it's getting in. Take the transformer out and the board is back to around 109v. Tried 2 new transformers, 2 new control boards, new run capacitor, exact same results. Tried jumping red and green, nothing. Tried bypassing cover safety switch. Condensate pump float switch isn't tripped, breaker, wall switch, everything is looking good. Fan spins freely by hand. Board fuse is good but tried 2 others anyways. New air filter too.
Plugged in a 24v transformer to the wall to bypass the board, relay clicks once, board led blinks slowly 10x at a time, but nothing else happens. Diagnostic codes says that means line voltage polarity reversed. Tried reversing lines but does the same code.
I think I've covered most of the bases and am looking to see if there are any other options. Any input is much appreciated! Thanks
Furnace model: C33-25B-2F-6
Serial: 6012E44238
Plugged in a 24v transformer to the wall to bypass the board, relay clicks once, board led blinks slowly 10x at a time, but nothing else happens. Diagnostic codes says that means line voltage polarity reversed. Tried reversing lines but does the same code.
I think I've covered most of the bases and am looking to see if there are any other options. Any input is much appreciated! Thanks
Furnace model: C33-25B-2F-6
Serial: 6012E44238
