29 year old furnace was working fine until this morning. The circuit board was replaced just 4 years ago, thanks to info from here. I opened the top part of the furnace and checked to make sure there was power. Then, I checked to see if the fan was free spinning and it was. When I pushed on the door power switch, I can hear the relay on the circuit board clicking. I checked the the voltage going to the motor and it fluctuated between 20.0 and 0.00 volts? Also after unplugging the motor from the circuit board leads, the buzzing/humming noise seems to be coming from a small transformer just below the circuit control board. It’s never made that noise before. I checked it’s output and it 25 volts, which is what it says it should be on the schematic (115 to 24 volts). I’m guessing that if it’s putting out the correct voltage that it’s also getting the correct voltage coming in. So does that leaves the board itself?
Thank you very much.