We had a significant rattle from the fan motor in our rear air conditioning unit. While the motor was turning freely the shaft was able to slide from end to end horizontally through the motor more than it should and that would generate a wobble when spinning. The vibration was so bad we could feel it in our body, the bathroom mirrors and the sliding glass closet doors were rattling worse than driving the rig. It was clearly something that would need to be addressed before more damage ultimately would occur.
This project took me about 1 hour and only two trips up and down from the roof. This is not intended to be an all-encompassing how-to guide. This is a potentially dangerous project given the electricity that may be retained in parts of the unit, even when there is no source of power connected. I am providing this as documentation of how I did this and am noting to my future self what to remember. I take no responsibility for your project and the results of it.
Both of our air conditioners are Dometic Penguin low-profile heat pump air conditioners, model #630515.331D, part #991761221.
The specific motor used in the unit is an A.O. Smith, model #F42E85A61, (a/k/a #3308039.019) which amazingly is still readily available now more than a decade after the original manufacturing. This motor appears to be available on Amazon for over $200 now. I acquired it from an eBay seller which was very quick and was less than $100 ($69 + $18 shipping) for the part. The eBay version did not come with a new foam ring on the shaft for filling in the airbox.
The only other minor part needed was a way to terminate the yellow wire (medium speed) to prevent any grounding of the wire.
The tools needed for this project are pretty straightforward. The wiring is mostly just plug and play (with pre-determined ends) with the exception of the yellow wire that needs to be insulated. The motor is mounted with three different bolts and nuts. The electrical box and fan shroud have some mounting screws. The one thing I did not anticipate was having the need for a proper hammer.
An air conditioning unit consists mostly of two major components, the compressor for magically cooling (or heating when in heat pump mode) and the fan motor for moving air through the coils. There are two “squirrel cages” mounted to the fan motor on a shaft that goes through the motor. The compressor, associated components, and the fan are all wired into the electrical box. In the electrical box is a circuit board and supporting electronic components for managing the voltages. One of those is a huge capacitor that can retain electricity for days, so be careful!
The basic steps include removing the power by turning off associated circuit breakers to both A/C units. Removed the outer shroud, each of the fan box components (the exterior fan box has two screws holding it in place), and the cover from the electrical box. I cut the wires from the old motor, leaving the wires in place to remember where to put the new wires. Removed the motor (3 bolts and nuts) from the chassis. Marked the distance from the end of the shaft for each squirrel cage and removed the cages. Then put the cages back on the new motor and reversed the process to re-assemble. The wiring required the removal of the grommet so that the new wiring could be put into place.
There is always an oops or two, and some blood, associated with every project. Besides slitting my wrist on the sharp aluminum fins of the exterior coil you have to work over, I wired the unit wrong and forgot to lace up the compressor motor wires.
THERE ARE TWO BLACK WIRES IN THIS PROJECT, MAKE SURE TO KEEP TRACK OF WHICH GOES TO WHERE!
The next morning I had to go back up on the roof to double-check that I had laced up the compressor wires and I had not done that. Fortunately no damage from either mistake.