Had a gas goodman gmpn furnace with 24 volt reading @ gas valve but wouldnt open. Tech support said to put direvt 24 volt to gas valve. I did and it opened. Why. I bypassed all switches and he said board or bad contact in a switch would cause amps to be weak but still have proper volts . Never seen this b4 . If i read 24 at a part that wouldnt work i would replace the part.