Air conditioning compressor motors are very simple to diagnose but can be confusing. If you find that an AC compressor is getting the proper voltages, has a good capacitor, and will not run or is tripping the circuit breaker, it could be that the motor windings are the problem.
There are only 3 motor winding failures:
Open Winding – This is when one of the wires that make up the motor windings is broken or separated.
Shorted Winding – If the insulation on the windings has failed, sometimes one part of the winding is making electrical contact with another part of the winding.
Grounded Winding – This is similar to the shorted winding but the wire with the broken insulation is making electrical contact with the compressor casing or ground.
Here is how to check the compressor motor if you suspect it has failed;
- Disconnect power
- Remove the top of the outdoor condensing unit
- Unplug the 3-prong plug on the compressor
- Set your multimeter to ohms
- Measure and record the resistance (ohms) measurement of each winding……just like this video is trying to demonstrate!