Like most gas appliances, a gas refrigerator uses a thermocouple to monitor the pilot light. The thermocouple converts heat energy from the pilot light into a small electrical current. The electrical current opens a solenoid valve, allowing gas to flow to the appliance. If the pilot light goes out, the thermocouple rapidly cools, cutting off the current to the solenoid. This causes the valve to close, preventing gas from escaping from the appliance. A failing thermocouple will keep the pilot light from staying lit, rendering the refrigerator inoperable. You can test a thermocouple on a gas refrigerator to determine whether you need to replace it.
Open the service panel to access the pilot light and thermocouple. On most refrigerators, the panel is under the front edge of the refrigerator or in a compartment on the back of the refrigerator. Consult the manufacturer's instructions if the panel isn't easily located.
Disconnect the thermocouple wires from the terminal block or switch. The wires should slide off the terminals. Some refrigerators use screw terminals. To remove the wires, loosen, but don't remove, the terminal screws with a Phillips- or flat-head screwdriver. Slide the wires out from under the terminal screws.
Set a digital multimeter to the DC millivolt scale. For auto-ranging meters, set the meter to the DC scale.
Connect the test leads from the multimeter to the wires from the thermocouple. If the thermocouple only uses one wire, connect that wire to the red or positive test lead. Connect the other test lead to a metal part of the refrigerator frame.
Turn the gas control knob to the "Pilot" position. Press the knob in and hold it for 30 seconds. Press the igniter button until the pilot light ignites. Continue holding the knob in to bypass the thermocouple.
Look at the thermocouple. The tip of the thermocouple should sit in the blue part of the pilot flame. If the thermocouple is off center, release the knob and turn it to the "Off" position. Allow the thermocouple to cool, then position it so it will be in the center of the pilot flame. Light the pilot flame and continue testing the thermocouple after you center it properly.
Hold the pilot knob in to keep the flame lit while the thermocouple is disconnected. Allow the thermocouple to warm up in the flame for 30 seconds.
Look at the display on the digital multimeter. The multimeter should read a minimum of 20 millivolts from the thermocouple. If there is no reading, check the connections to the meter and test the thermocouple again.
Replace the thermocouple if the reading is below 20 millivolts when heated.