Things You'll Need
A Trane gas furnace has a thermocouple that is attached to the pilot light. The job of the thermocouple is to sense whether or not there is a flame and to stop the flow of gas if there is not a flame. The thermocouple attaches to a fitting on the gas line at one end and to the pilot light orifice at the other. Replacing the thermocouple on a Trane gas furnace is accomplished in less than half an hour.
Shut off the gas supply to the furnace using the main gas shutoff valve or a shutoff valve that is closer to the furnace, if one is available.
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Remove the access panel from the front of the furnace using a Phillips screwdriver.
Locate the thermocouple which is attached to the pilot light. Trace the thermocouple to where it attaches to the gas line.
Unfasten the fitting of the thermocouple by turning it counterclockwise with an adjustable wrench.
Pull out the other end of the thermocouple from the pilot light once the gas line end has been completely removed.
Stick the steel tube end of the new thermocouple into the pilot light where the old one was removed. When you purchase the new thermocouple, ensure that you get the correct length.
Fasten the fitting on the copper end of the thermocouple to the fitting on the gas line by hand. Ensure that the fitting is attached evenly to avoid cross-threading. Tighten the fitting with an adjustable wrench. Replace the access panel and turn on the gas supply. Relight the pilot light by following the instructions on the particular Trane furnace that you have.