How to Troubleshoot a Gas Log Fireplace Thermocouple

Check the gas log thermocouple connection on the gas valve. Untwist the thermocouple from the valve. Wipe the threads on the thermocouple’s connector with a soft cloth and re-install it. Tighten it with your fingers and turn it an additional one-eighth of a turn with an adjustable box wrench. If the thermocouple is too loose or too tight, the valve won’t receive the signal from the thermocouple to keep the gas flowing to the pilot, and thus the pilot will go out.

Verify the tip of the gas log thermocouple sits directly over the pilot flame. Move the thermocouple until the pilot flame heats the tip of the thermocouple. If the flame hits the thermocouple anywhere else, it can’t send a signal to keep the gas valve open.

Inspect the thermocouple from the pilot assembly to the gas valve for damage. If the line is kinked, crushed or bent, you must replace the thermocouple in order for the valve to receive a signal.

Clean the tip of the gas log thermocouple with emery cloth to remove any white carbon buildup on the tip of the thermocouple. The carbon won’t allow the tip of the thermocouple to heat and send a signal to the valve to supply gas to the gas log set.