Turn the AC off and disconnect power
Inspect the compressor for visible damage, oil leaks, or burnt wiring
Check the breaker, fuse, and disconnect for proper operation
Set the multimeter to measure voltage
Verify the compressor is receiving the correct supply voltage
Check the capacitor for bulging, leakage, or failure
Test the capacitor with a multimeter or capacitor tester
Measure compressor winding resistance between the terminals
Compare the winding readings for continuity and balance
Test each terminal to ground for continuity
Replace the compressor if any terminal shows continuity to ground
Check the overload protector for continuity
Test the contactor for proper closing and power delivery
Measure compressor amperage during startup and operation
Compare the amp draw to the nameplate rating
Listen for humming, clicking, or repeated starting attempts
Check refrigerant pressure if the system is running
Verify the compressor starts and runs smoothly
Confirm discharge line temperature rises during operation
Use a megohmmeter if insulation failure is suspected
Replace faulty components before retesting the compressor