Design & DIY

Appliance pilot light won’t stay lit? Blame the thermocouple

Photo by Meaw_stocker/Shutterstock

Thermocouples play a vital role in the safe operation of older gas appliances, such as water heaters, ovens, fireplaces, and fridges. These small yet indispensable devices ensure that the pilot light remains lit, which, in turn, allows the appliance to function correctly.

In a gas appliance, the pilot light heats one end of the thermocouple while the other end remains cooler. This temperature difference creates a small electric current that keeps the gas valve open, allowing the flow of gas to the pilot light. If the pilot goes out for any reason, the thermocouple cools and shuts off the gas supply, preventing any potential hazards.

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Even though thermocouples are pretty tough and have no moving parts, they can sometimes become faulty due to debris accumulation, misalignment, or oxidation on the metal surface. If you have a pilot light that won’t stay lit, a malfunctioning thermocouple could be the culprit. There are a couple of things you can try before getting a replacement.

First, check that the thermocouple’s tip is immersed in the flame. It should be positioned to get as much heat as possible.

Second, clean the thermocouple and pilot assembly. Use a soft cloth or fine sandpaper to remove any built-up dirt, soot, or oxidation that could interfere with the thermocouple’s ability to heat up in the pilot flame. If the tip of the thermocouple is visible and accessible, it’s an easy job. If it’s hard to reach, you may have to partially disassemble any metal heat shields or casings that are in the way.

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If the pilot light still won’t stay lit after cleaning or lightly sanding, it’s likely time to replace the thermocouple. Most
cottage hardware stores carry universal thermocouple kits. Bring the old one with you. Thermocouple kits come with a few mounting options; pick the one that matches your appliance.

This article was originally published in the September/October 2023 issue of Cottage Life.

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