Turn off power to the AC unit at the breaker
Verify power is off with a non-contact voltage tester or multimeter
Remove the access panel
Take a clear photo of the capacitor wiring
Discharge the capacitor using an insulated resistor or insulated screwdriver rated for the task
Disconnect the capacitor wires
Set the multimeter to capacitance mode if available
Place the meter leads on the capacitor terminals
Read the capacitance value on the meter
Compare the reading to the capacitor’s rated microfarads
Replace the capacitor if the reading is outside the tolerance range
If capacitance mode is not available, set the multimeter to resistance mode
Touch the leads to the terminals and watch for a brief low reading that rises toward infinity
Check between each terminal and the metal case for continuity
Replace the capacitor if there is no expected charge response or if there is continuity to the case
Reconnect the wires exactly as photographed
Reinstall the access panel
Restore power and test the AC unit