Tips For Cleaning And Testing A Furnace Thermocouple

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Do you have a gas furnace that is not starting? The likely problem is a dirty thermocouple. The thermocouple is essentially a safety mechanism that helps monitor the furnace's pilot light. The thermocouple opens the furnace's gas valve once the thermocouple is heated to the proper temperature to burn fuel. If the thermocouple is covered with dirt, it will never open the gas valve and the furnace will not start. Here are some tips for cleaning and testing this crucial part of your furnace. 

Locating The Thermocouple

The thermocouple can easily be identified by following the gas line that runs into your furnace. The gas line will run into the ignition switch, which then has a small tube that goes to the pilot assembly. The pilot assembly houses both the thermocouple and the pilot burner. The pilot burner bends and fans outward at the end, and the thermocouple will look like a thin cylinder that is located right next to the pilot burner. 

Cleaning The Thermocouple

A dirty thermocouple will not allow the part to get hot enough to activate and turn on the gas. To clean this part, you'll need to shut down the gas and power, then turn off the furnace at the ignition switch.

An adjustable wrench can be used to disconnect your thermocouple from the pilot assembly, or your thermocouple may be unscrewed by hand if it is loose enough to do so. You can use an emery cloth to wipe down the outside surface of the thermocouple, which should be enough to clean the soot off the part.

When finished, you can place the thermocouple back into the housing assembly. Turn on the electricity, gas, and ignition switch in that order, and you should be ready for the next step.

Testing The Thermocouple

The ignition switch has a bypass button that allows you to open the gas valve to test the thermocouple. You need to hold the test button down and light the ignition manually with a long stick lighter. Keep the gas valve open for about 30 seconds before switching the gas valve to the on position, which should be enough to heat the thermocouple. Turn the thermostat on to heat mode and see if the furnace keeps running. If the thermocouple is bad, the furnace will shut down by telling the ignition switch the burner is not hot enough to ignite the gas. 

If your thermocouple fails this test, contact a local gas furnace repair services contractor for help replacing the thermocouple with a new one. 

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28 July 2019

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