Furnace Pilot Light Keeps Going Out

If you notice that your pilot light keeps going out during the cold weather, you’re not alone. Local HVAC professionals will tell you it’s a fairly common problem.

Fortunately, there’s no reason to panic. The pilot light going off frequently doesn’t pose any significant danger to you and your family. The only thing it may cause is inconsistent heating. The good news is – that’s also something you can diagnose and fix with ease.

What’s a Pilot Light?

The pilot light is a small flame kept in certain gas-fired heating appliances, such as the furnace, water heater, and gas fireplace. Its sole purpose is to help light up the main burner without the need for a matchbox.

When you turn on the heating appliance, gas flows to the main burner, and the pilot light automatically lights up the burner. So it’s a very efficient appliance lighting mechanism.

The pilot light isn’t supposed to go off. It’s designed to remain ON for the rest of the heating season so you can re-light your heating appliance with ease. However, sometimes you may wake up to find that it’s no more. You’ll notice it’s gone off because the flame is visible when the pilot light is ON. When it goes off, the flame dies out.

4 Reasons the Pilot Light May Go Off

The following are common reasons a pilot light may go off and what to do about it. Remember to shut off the gas heater and wait at least five minutes for the gas to disperse before diagnosing the pilot light.

1. Dirty Thermocouple 

Whenever the pilot light goes off, the most likely culprit is a dirty thermocouple. The thermocouple is a device that measures indoor temperature and uses the measurements to regulate gas flow inside your furnace or other gas heating appliances. It has two wires, one located near the thermostat and another by the pilot light flame.

The side located next to the pilot light is the one that signals the gas valve to open or close. If it bends away from the flame, perhaps due to improper use, it won’t register heat and will keep the gas valve closed. Thermocouples can also collect dust and debris, thus malfunction.


Ensuring regular maintenance is an effective way to protect the thermocouple from being or building up dirt and debris. This can go a long way in preventing the pilot light from going off.

However, if the light is already off, it’s best to call the experts. You can attempt to clear the debris and dirt. But keep in mind that the thermocouple is also a delicate component. An HVAC professional knows how to clean it and reposition any bent wires gently.

2. Blocked Pilot Opening 

Your pilot light opening is a small hole that allows gas to pass through to keep the pilot light alive. However, over time, this opening may become clogged and partially blocked due to dirt accumulation. It may even become blocked entirely.

Common signs that your pilot light opening has blocked include a weak flame and gas not coming through it. You can verify both. If you recall the pilot light being small and yellow a few days before the light completely went off, then there’s a blockage. The same applies if there’s no gas hissing out even when you turn off the furnace as you attempt to light the heater.


You can safely attempt to remove the dirt buildup to restore pilot light function. Turn off the gas supply and gently extract the debris and dirt, blocking the pilot hole using a thin needle. Once you’ve removed all or most debris, turn the gas supply back on and light up the appliance to see if it works. It should have a light blue flame in a cone shape.

If the light is still weak and yellow, it’s most likely not an issue of a clocked pilot opening. Consider calling the professionals.

3. Poor Air Circulation 

The heating appliance is supposed to be located in an area with unrestricted airflow. That’s because it needs oxygen for combustion. When there’s a shortage of oxygen supply, it becomes to sustain a healthy pilot light. The flame will become characteristically weak and may eventually die out.

The air around the furnace may run out of oxygen for the same reasons other home areas usually have carbon monoxide poisoning. For instance, a poorly ventilated area may soon run out of oxygen. The same can happen if the furnace is installed in a small, enclosed area. Above all, oxygen depletion sometimes happens because of inefficient burning.


The first solution here is to install an oxygen depletion sensor at hand. Never run a gas heater without an oxygen depletion sensor. The sensor will sound an alarm whenever low levels of oxygen are detected in the area.

Just as important is the need for proper installation and ventilation. This is one of the main reasons you should always go for professional gas heater installation. The location, positioning, and ventilation are all important. Scheduled professional maintenance will also help you uncover and address issues related to poor air circulation in your home.

4. Furnace not Getting Enough Gas

Yes, it happens. And, when the furnace isn’t getting enough gas, it’s impossible to keep the pilot light on. Why would the furnace not have enough gas? There are several reasons.

First, maybe there’s no gas supply. If you use propane gas, perhaps the tank is empty. For natural gas users, maybe your supplier has issues. Another common reason is dirty filters. Filthy filters can restrict or block supply to the heating appliance. A bad gar regulator can also block gas flow into your home. The regulator is typically located outside the house on the gas meter.

Finally, the reason your furnace isn’t getting enough gas could also be a malfunctioned or damaged thermostat. The thermostat is the heating system’s brain. It tells the furnace what to do and when. If it’s broken, it may fail to communicate to the heating system to release gas.


Unfortunately, gas flow issues are a bit tricky to diagnose if you’re not a licensed professional. Attempting to check gas supply on natural gas lines, for instance, is strictly prohibited due to the inherent risk. You may even be fined.

So, the best solution is to contact your HVAC services provider. Whether you think it’s a faulty thermostat or wish to check whether your propane tank is empty, consider calling an HVAC professional.

What Else Should You Know?

Sometimes the pilot light may also go off for complex reasons, such as a complication in the circuit board. We didn’t list this among the main factors because a malfunction in the circuit board is rare and typically affects the entire heating system. It’s also a very delicate matter that you matter that must strictly be left to the professionals.

If you have diagnosed the thermocouple, pilot opening, poor air circulation causes, and common causes of insufficient gas supply, it might be time to consider the circuit board. Don’t attempt to open the heating system to check the circuit board, though. Instead, shut off the gas supply and contact your preferred HVAC professionals.

Ultimately, the issue should be restored without much fuss – unless it’s the circuit board that can take much longer to fix. Repair costs depend on the underlying issue.