A Thermal Coupling furnace is a device that is used to help control the flow of gas in a gas-powered furnace. The thermocouple is located near the gas valve in the furnace. Furnace thermocouple parts sense the pilot light's temperature as soon as the furnace is turned on To prevent a gas leak, the thermocouple will shut down gas flow if the pilot light goes out. If the thermocouple for furnace is not functioning properly, it can prevent the furnace from turning on or cause it to turn off unexpectedly. It is important to have a functioning thermocouple in a gas furnace to ensure the safety of the appliance and to prevent the risk of a gas leak.