I have a Goodman furnace model number GMPN 100-4 that hums when the thremistat calls for heat. The status light on the control board is on solid and the transformer seems to hum, is the transformer bad? Any place I can find out what the voltages should be reading on the transformer inputs and outputs?
BTW the AC works fine but the heat doesn't turn on anything, not the blower or the flame.
Thanks for any input you can give me.