Last night my AC stopped working. No air was coming out of the vents. Earlier in the night I had noticed a whining sound every once in a while emanating from my mechanical room. I have a lot of computers in the next room as well so I wasn't sure if the noise was coming from one of them or not. As I was listening more closely, a loud, final screech came from my furnace in the next room. I immediately turned off the AC at the thermostat and also tripped the breaker to OFF. I opened the furnace and removed the fan/motor unit. I tripped the breaker back to ON, turned the AC fan to ON at the thermostat, walked back downstairs and listened to the blower motor. The fan was not turning in the squirrel cage and the motor was making a humming sound. Figuring this was the source of my problem I went ahead and turned everything back off, removing power to the furnace and disassembled the fan/blower unit so that I could take the motor in for replacement this morning. I also replaced the capacitor. Everything seemingly went very smooth.
The old motor was an Emerson 3-speed K55HXJYZ-5490. The new motor is a GE 5KCP39FGM421 2-speed. I have no idea if this is the proper replacement, and I am beginning to wonder if the guy at the wholesale supply place does either. I can't get the new motor to power on. I replaced the capacitor first. From the new motor I:
- connected the brown and brown/white wires to the capacitor
- connected the black wire to the black feed from the furnace (same as with the Emerson)
- connected the white wire marked as "LINE" on the GE wiring schematic to the red wire from the furnace (blue wire on Emerson was connected to this red wire)
- used a plastic cap to close the red wire from the GE motor (the red wire on the Emerson was also capped this way)
- connected the white wire from the furnace to the capacitor
After connecting all of the wiring I closed up the wiring box and put the blower/fan unit back in its housing at the bottom of my furnace. I tripped the breaker back to ON, set the thermostat to a low temperature and flipped the fan control to ON. I expected the blower to come back on immediately. It did not. I returned to the mechanical room and could hear a light buzzing emanating from the furnace (not from the blower motor area but up above that, near the heat exchanger). I waited 10 minutes but the blower never kicked on. I could hear the AC unit outside my house working.
Thinking maybe I had the wiring incorrect I swapped places between the red and white wires coming from the GE motor, connecting the GE red to the furnace red and capping off the GE white so that it was not connected to anything. Still nothing came on.
What could be the problem? Surely its not a bad board. I don't even see what looks like a motherboard anywhere. I do see a closed metal box from where it appears all of the furnace wires emanate. I'm guessing that's the board. It's just that considering I heard all this noise before the AC stopped, I'm pretty sure the problem is the blower motor not the board. I've heard these types of motors seize before (used to work in a motorcycle shop) and that is what this sounded like.
Old Emerson wires
Old Emerson wire connections to furnace inside wiring box:
What may or may not contain the "board":
Old capacitor from top:
New GE motor box label:
New GE motor wiring schematic:
Some Honeywell unit in the furnace:
Old Emerson motor wiring connections to furnace: