Why Does My Pilot Light Keep Going Out On My Furnace

A common issue you may experience with a gas furnace is when the pilot light keeps going out. This pilot light problem has a few different causes. When the problem occurs, something to look at is the thermocouple and the furnace pilot light itself.

Keep reading to know why your furnace pilot light keeps going out and how to resolve the issue.

Why Does My Pilot Light Keep Going Out

If the furnace pilot light keeps going out, the culprit is probably one of the following reasons:

Broken Thermocouple

The thermocouple on your gas furnace is a small device used to test the temperature of the pilot light flame. This small part sits right in front of the pilot light. It contains wires inside that become heated when the furnace lights.

The thermocouple’s wires produce a specific voltage when they come into contact with heat. This voltage is recorded and interpreted. If it senses that the pilot light is lit, it will allow gas to flow through the supply valve. When it senses that the pilot light is off, then the supply valve is shut. This process keeps gas from flowing through the supply line when the pilot light is not on. 

Thermocouples will wear down over time and become more sensitive than they should. They also may stop working entirely and keep the gas supply valve closed at all times. If your unit is old or if you had no idea when it was last changed, then try replacing it to fix your pilot light problem.

Replacing a broken thermocouple is cheap and relatively easy. This is how to replace the furnace thermocouple.

Thermocouple are wired into your furnace system. You can find the end of the device sitting right in front of the furnace ignitor. The device will look like a round tube. Locate the tube and use a wrench to release the nut that keeps the tube secured in the mounting bracket.

Pull the tube out of the bracket and also release the wired end from its attachment. Purchase a new thermocouple that matches the old one. Slip the new device into place, making sure the tube end sits upright. Screw tightly the nut back into it’s socket and plug the wiring in. 

Once the new thermocouple is in place, test the unit to see if the pilot light stays on.

Dirty Pilot Light

Sometimes the pilot light will not stay lit because there is a great deal of dirt, soot, and other debris around the light opening. You can remove some of the debris to see if this resolves the problem.

You would need to allow your heating unit to cool down completely if the system was recently running. Afterward, remove the front cover from the unit. Look for any flakes or rust that may have accumulated inside. Use a shop vacuum to remove the debris.

Also, locate the pilot light. It may sit on the bottom of the unit, or it may be located closer to the top of the device. This depends on the type of heater you have. 

Inspect the pilot light and look for black or brown accumulations of debris. If you see these, then use a wire brush to lightly scrub them away. Metal files work well to clean away debris that is difficult to remove.

If you notice stains, then use a bit of rubbing alcohol to release them. Alcohol is also a good choice around the opening of the pilot light, so gas can flow freely.

When you complete your furnace cleaning, look for signs of pits, holes, or breaks around the pilot light. If you see these things, then they should be replaced.

Accessing the thermocouple and the furnace pilot light will require removing your furnace’s burner assembly; we suggest having a professional clean the pilot light.

Another reason why the furnace pilot light keeps going out is high gas demand. It is being unlikely but possible, high natural gas demand causing system fluctuations.

If you feel uncomfortable doing any of the things noted above, call an HVAC technician to do the task. They will quickly and efficiently take care of the furnace pilot light problem. The goal is to keep the pilot light lit and burning to provide ignition for the main burners.

About Mas Broto

Have been in the heating and air conditioning (HVAC) industry for over 20 years. He is person that will grow and thrive to learn more about the HVAC industry throughout his career. Mas Broto is also a blogger, who's dedicated to bringing you the best knowledge to get ahead in the game of life.