Furnace Pilot Light Keeps Going Out Thermocouple

If your furnace pilot light keeps going out it s likely you have a broken thermocouple in your gas furnace.

Furnace pilot light keeps going out thermocouple.

If you can t get the flame to light at all and you re sure the gas is on there s probably an obstruction in the pilot tube. The thermocouple is a rod that comes into physical contact with the flame in your system. There are various instances that may cause the thermocouple to not detect the flame in your gas furnace. The pilot orifice may be full of dirt.

The number one reason why the pilot light keeps going out is the thermocouple. The pilot light must heat the thermocouple so the thermocouple can keep sending an electrical charge back to the furnace which keeps the gas valve from shutting closed. The biggest reason a coleman furnace pilot light keeps going out is the thermocouple is placed too far from the pilot light. If the flame lights and goes out when you release the gas control knob after holding it in for the recommended 20 to 30 seconds that s the sign of a thermocouple malfunction.

This is the pilot flame that provides the heat. A bad thermocouple itself can prevent a gas furnace or boiler from working if you can light the flame at the pilot manually but then the flame goes out when you release the manual gas feed valve the thermocouple is probably bad. But if the orifice is dirty or restricted the pilot light won t light properly. The thermocouple is a sensor inside a steel sleeve that sits in front of the pilot light.

Thermocouples work by producing a small amount of voltage when it is heated. The pilot light is supposed to be a strong blue cone not a weak yellow flame. Which means the thermocouple will shut off the gas flow to your furnace as a safety measure. Cleaning out the pilot orifice means disassembling the pilot and clearing out the debris using a needle or compressed air.

The pilot light needs a strong flow of gas to make a strong steady blue flame that the thermocouple can sense. Either the thermocouple is going bad or it is dirty and needs to be cleaned. A weaker flame won t envelop the thermocouple properly.