How to Check a Refrigerator Relay Assembly

Unplug the refrigerator power cord and move the appliance away from the wall to gain access to the back.

Locate the compressor inside the cavity underneath the black evaporator coils on the back of the refrigerator. Look for a small black tubular device called a “capacitor” attached to the motor with a couple of wires leading to the relay box mounted on the side of the compressor. If you see a capacitor, the refrigerator is fitted with the older type mechanical relay.

Discharge the capacitor as described in the following two steps to avoid receiving a painful high voltage shock when you touch the capacitor wires.

Disconnect the two spade connectors from the capacitor with insulated needle nose pliers. Connect two leads fitted with alligator clips on both ends, to the wires leading from a 20,000 ohm wire wound resistor. Attach the alligator clips on the other end of the leads, to two separate screwdrivers.

Hold the screwdrivers by the insulated handles. Press the tips of both screwdrivers against each individual terminal on the capacitor without allowing the screwdrivers to make contact with each other. Maintain contact for 6 to 8 seconds. Remove the screwdrivers and wait 30 seconds, and replace the screwdriver tips on the capacitor terminals for another 5 seconds to ensure that it is completely discharged.

Pry the lid off the compressor relay box to reveal the start relay and the motor overload protector connected to two terminals on the side of the motor. If the start relay is a shiny black tubular device, it’s an inexpensive solid state relay. Pull it out, detach its slip-on connector between the relay and the compressor, and replace it; solid state relays are cheap enough. If the start relay is wound with thick copper wires, it’s the older, more expensive type. Go to the following step.

Grasp the sides of the start relay and pull it straight out of the compressor. Grip the relay end of the slip-on connector between the relay and the compressor with the needle nose pliers, and carefully withdraw the terminal. Inspect both the connector and terminal for corrosion, if either is corroded, they must be replaced.

Set a multimeter to the X1 ohms setting. Invert the relay to disconnect the internal magnetic switch. Place one of the Multimeter probes into the hole on the white plastic base marked “S,” and the other probe into the hole marked “M.” Check the Multimeter display, it should read zero ohms to indicate continuity.

Leave the probes in place and turn the relay over to the vertical position; you will hear a faint click as the magnetic switch engages. The Multimeter should now display an ohm reading of infinity.

Invert the relay. Insert one of the probes into the “S” hole on the plastic base and touch the other probe to the metal terminal on the side of the relay marked “L.” Once again, the display should show Zero ohms. Turn the relay right side up and repeat; the ohms readout should now be infinity.

Invert the relay once more and Insert one of the probes into the “M” hole on the plastic base and touch the other probe to the metal terminal on the side of the relay marked “L.” The reading should be zero ohms. Turn the relay right side up and repeat; the reading should remain at zero ohms to indicate continuity.

Replace the relay if it fails any of the above tests. If the relay passes all the tests, the compressor itself may have burned out. If this is the case, schedule a service call and ask the technician to diagnose the fault and carry out any necessary repairs.