Test the compressor relay for continuity using a multitester. Set the multitester to the ohms setting X1.
With the relay upside down, place the probes into the terminals labeled "S" and "M". The multitester should display a reading of zero ohms, indicating continuity (or if using a continuity tester, it should light up).
With the probes still in place, turn the relay over. You should hear the click of the magnetic switch engaging. The multitester should now display an ohm reading of infinity (or the tester should not light up).
Turn the relay upside down again, place the probe on the "S" terminal and place it on the side terminal labeled "L".
The multitester should now display a reading of zero ohms (continuity). Turn the relay over and the reading should change to infinity.
With the relay upside down place one probe on the "L" terminal and the other probe on terminal labeled "M".
The multitester should display a reading of zero ohms. Turn the relay over and the reading will stay the same, zero ohms.
If the compressor relay does not pass all of these tests, it should be replaced.