Troubleshooting a Furnace Pilot Light: Common Causes and Solutions

It may be frustrating when you try to turn on your furnace only to discover the pilot light won’t light. I’ve been in the same situation. It was the start of winter and I tried to turn on my furnace 3 days after we got some water in the basement. It sounded like it turned on but then quickly turned off.

The most likely reasons your pilot light will not light up again are that the thermocouple was replaced improperly, there was a flood that permanently affected the pilot light, the pilot light orifice is dirty, there’s a broken gas valve, or a broken gas regulator. Common fixes are adjusting the thermocouple, cleaning the pilot light, or replacing the gas valve. 

The first thing you need to do is figure out why the pilot light is not working. Then you can try some fixes. 

Be sure to take safety precautions such as turning off the gas before repairing, replacing, or cleaning. Some tools you may need are a screwdriver and an adjustable wrench. Now let’s get into it.   

What’s The Purpose of a Pilot Light?

A pilot light is a small flame. This flame is what heats your furnace when you want heat. The pilot light resides at the bottom of your furnace. It is attached to a gas valve that can be switched on and off. Pilot lights are only on gas furnaces and not electric ones.

The pilot light is essential for heating the burners of your furnace. Without the pilot light, the burners will not be heated. Meaning that you will not be able to get heat because the furnace will not get hot. 

Most pilot lights are usually constantly burning. Some will turn off when heat is not needed and ignite when you turn on the heat. It is possible that your furnace’s pilot light must be lit manually with a match or lighter. More advanced furnaces will have the pilot light ignited electronically. 

In warmer months the pilot light should be off. This is because you don’t need heat in the summer or parts of the spring. When it is off, dust and debris can build up. Although there may be a bigger problem, a dirty pilot light is the most common reason it doesn’t turn on.

Why Is Your Pilot Light Not Working? 

It may not be working because of a dirty air filter, the thermocouple alignment, a dirty pilot light orifice, a broken gas valve, or a broken gas regulator. When your pilot light is not working, you may start to panic, but there is no need to. It is a common problem.

Your Air Filter is Dirty

Air filters can accumulate dust and debris. When it is not cleaned regularly or replaced when needed it will cause the pilot light to not work. A dirty air filter will also cause your utility bill to rise and may sometimes cause your unit to produce no heat even if on the heat setting.

The air filter in a furnace is needed to keep fresh air flowing through the system. With a dirty air filter, the fresh air will not be able to flow properly. Meaning that the pilot light will not ignite or it will turn off again and again. It does this because there is not enough oxygen getting to the  flame.

The Thermocouple is not Aligned

The thermocouple must be aligned properly for the pilot light to be on. A misaligned thermocouple means that the pilot light will not ignite. This is a safety precaution taken by furnace manufacturers. It shuts down the gas supply when it is not properly aligned. This prevents fires and explosions.

Your furnaces thermocouple can become misaligned because it has gotten old. It can get bent from its position or become damaged without your knowledge. If you have had your furnace for a long time it is possible for the thermocouple to get misaligned. 

Your Pilot Light Orifice is Dirty

The pilot light orifice has control over the flow of gas in a furnace. It is a sensitive part and will malfunction when there is even a small amount of debris. It is a safety precaution so that it does not start a fire. 

If you sense that the pilot light is turning on but not working enough then you should check it. To be able to tell if it is dirty you may need to open the access to the pilot light. Try to light the pilot light. If you see that the light is a warm yellow color then this is an indicator that the pilot light orifice is dirty. The light should be a strong blue color.

The Gas Valve is Broken

A sign that the gas valve is broken is that the furnace does not turn on at all. If it is broken it will not have any gas run through it. This is because if there is gas running through a broken valve then it will leak into your home. A gas leak is a serious problem that can cause health issues. Generally, most gas valves will completely shut off if it detects a problem. 

This affects the pilot light because the pilot light needs gas to function. Without gas, it can’t stay lit or be lit. Gas will not reach the pilot light when you turn on the heat. The gas valve may just be stuck or have other issues than being completely broken.

Your Gas Regulator is Broken 

The gas regulator regulates the gas entering the furnace. This way it can send in the correct amount of gas when you turn on your furnace. The regulator measures the gas with pressure. If the gas regulator is broken or malfunctioning then it can not regulate the gas entering the furnace.

A broken gas regulator affects your furnace’s pilot light because it will not allow gas to flow. Without the flow of gas, the pilot light will not ignite. It is another safety precaution in furnaces to prevent a gas leak or fire.

How to Fix Your Pilot Light 

Some fixes you can try are cleaning your air filter, adjusting the thermocouple, cleaning the pilot light, or replacing the gas valve. After accessing the possible issues you will know which one you need to do. There are plenty of ways to fix your pilot light. Some of these fixes may need expert knowledge and experience. 

Clean Your Air Filter

To clean your air filter all you need to rinse it down. You may need a screwdriver or a new air filter depending on what type of filter you have. If your air filter is behind a panel then you need to unscrew the screws. In some systems, you may be able to just lift up the panel.

Once the air filter is reviled, slide it out. Take the air filter and rinse it down outside and rinse it with a hose. If you do not have a hose then try the shower or kitchen sink. Once you have thoroughly washed it, let it dry in the sun. After it has dried then you can put it back where you got it. 

If you have a filter with a cardboard frame then you will need to replace the filter. These types of air filters cannot be washed.

Adjust the Thermocouple

To adjust the thermocouple you will need an adjustable wrench and emery cloth. The thermocouple is located right next to the pilot light. Start by turning off the gas and letting it cool down so you don’t burn yourself. 

Use the adjustable wrench to get the thermocouple out of the furnace. Use the emery cloth to clean the thermocouple. Check the thermocouple for any bends or potential cracks. If you see it has any then you will have to replace it.

After you check it, you can put it back where it was. Tighten it in and start the furnace to see if it works.

Clean Your Pilot Light

To clean your pilot light you will need an air compressor. This will shoot puffs of air into the pilot light and clean out the debris. In order to do this you need to access the pilot light.

To get to the pilot light you will be able to take off the panel or use a screwdriver to take it off. Once you can see the pilot you should light it. This way you can compare the flame before and after using the air compressor. 

Make sure the pilot light is off and stick the air compressor in front of the pilot light. Give it a few puffs and be sure to have room so the debris can exit. Light it before closing the panel to see if the flame gets larger. If it does then you have successfully cleaned the pilot light.

Replace Your Gas Valve

To replace the gas valve start by opening the panel to the gas valves. You will need an adjustable wrench, a screwdriver, and a new gas valve before you start the repair. Replacing a gas valve is the most difficult fix there is. 

You will have to take off the whole gas valve and pipes attached to it. To do this, you need to unscrew the nuts with a wrench and disconnect all of the power cords. Unscrew the gas valve from the pipes and screw on the new one. Be sure to take off the plastic cover of the new gas valve. 

After you attach the new gas valve then you will need to reattach everything you took out. Start by screwing in the valve and pipes. Then you can reconnect the wires. Finally, you can use the wrench to tighten everything back.

When Should You Call a Professional

You should call a professional when you cannot find the cause or cannot repair the issue on your own. Along with if you feel uncomfortable working with a furnace. Furnaces are hard to work with and most times require expert knowledge and experience. Professionals know the absolute most about furnaces.

It can be dangerous for you to try to fix a furnace on your own. For example, you may not fully understand where a certain part is or how to properly fix it. You may also like the tools to properly fix the furnace. Don’t feel discouraged though, most people have to call professionals for help.


There are a bunch of reasons that your pilot light may not turn on. The problem all have solutions. If you suspect there is an issue you can run through how to fix the issue. There are plenty of solutions you can try. You now have expert knowledge on how to find and fix a pilot light. It is not as scary as it may seem so give it a try!