Servicing a dry bearing

At my father’s house today and I heard the heat pump chirping occasionally. To me, that is the sound of lubrication failure and an early state of electric motor failure. As compressors are hermetically sealed and lubricated, I was almost certain the culprit was the blower motor.

I opened up the unit and saw the blade still spun freely, a good sign. After shutting the breaker, I disconnected the compressor and powered the heat pump back up. The fan ran for about 30 seconds and started chirping again.

I proceeded to remove the motor. It is a 48Y frame 1/4 horsepower single phase motor made in 1989 by General Electric. Looking up the cost of this motor to be $160-180 in the 60C ambient temperature spec (the 40C was $60 cheaper, but would fail soon). Given the expense, I decided to experiment with servicing it.

Loosened the set screw to remove the blade. The motor has 4 long screws/nuts that hold the motor together and they were removed.  With a screwdriver, I carefully prayed the pot metal caps off each end. The armature slid out of the stator and gave access to the two sleeve bearings. I lubricated them with a grease that was convenient, but a heavy gear oil probably would have been more appropriate.

I reassembled the motor and electronically attached it to the heat pump circuit.  I decided to let it run for a while to see how it performs.  After about 30 minutes, it was warm, but silent, so I decided to end the test with a declaration of success.

The heat pump was mechanically and electrically reassembled and seems to be performing well with fresh lubrication.

Anybody curious what NEMA frames are, I attached a chart.