...or not to replace the board. That is the question.
I have a Carrier furnace, model 58PAV090-14, installed fall of 2000 (11 1/2 years old) Air conditioner works. Furnace does not. Weather has been cooperative. I've been able to make due for the past week and in a week or two probably won't need the furnace at all for another six months, so I'm in a position to futz around with fixing this.
The first symptom is the red LED is flashing continuously. It is normally on steady, no flashing. It is not providing any codes, just the rapid flashing. The legend on the door panel states the rapid flashing indicates reversed polarity in the 115V AC. Not sure why this would have changed spontaneously after 11 years. I have checked that the hot line is hot and the neutral is not, checked ground and reversed the leads to the control transformer following recommendations on another forum with no success.
Yes it's getting input from the thermostat. The thermostat can turn on the air conditioner. Also, if the furnace power is turned on while receiving Heat command from thermostat, the main blower turns on for 90 seconds and then turns off. It does this. Problem is that after the blower turns off, it should begin the ignition sequence. Nothing happens. No power (measured with multimeter) is provided to the inducer motor. And if the inducer motor doesn't turn, nothing else is going to happen. I tried to tap the relays to see if they could be freed up to no avail.
Physically, the control board (no. 1012-940-J HK42FZ009) appears undamaged. No sign of burned conductors. Fuse is still intact. However, some of the exposed component leads are covered in green dust that looks like copper oxide. Is that indicative of something?
Thirty years ago I used to work on multi-megawatt induction furnaces as big as my living room. Now I'm staring at this furnace the size of a big suitcase wondering what to do next (or dithering because I know but don't want to cough up the money)
Is there something else that can be checked or should I just change the board and be done with it?