Why Your Furnace Pilot Light Won't Stay Lit - Causes & Troubleshooting

A furnace pilot light drives your furnace's flame, especially if you have an older, natural gas-driven furnace. These operate based on a small blue light that appears when the furnace turns on. Its functioning is pretty simple. 

Natural gas is released into the burner through the valve when the furnace is turned on. When the natural gas comes in contact with the blue pilot flame, a real flame is made.

You'll find this technology easily observable in appliances like gas stoves. However, the workings of a pilot light in a furnace are also similar. A small amount of gas is usually released through a small tube, which ignites when lit. 

The pilot light, however, can be dangerous and risky. If the pilot flame dissipates, the gas coming from the tube (if it's not switched off) will collect in the air.

And if it were suddenly ignited by any means, all the gas in the air would be lit, which could cause an explosion. Of course, many devices that use this mechanism have safety nets that will troubleshoot this problem if it were to occur. 

However, if you're having problems where your furnace pilot light won't stay lit, the tips below could help you understand why. However, owning a gas-driven furnace is a pretty old venture, so the problem might be that you're using it before it's time.

Yet, if you want to repair your furnace and keep it going for a few more winters, we have some possible causes of furnace pilot light problems and some solutions listed below.

Causes of a Pilot Light That Will Not Stay Lit - Why Your Furnace Pilot Won’t Stay Lit

The following are some common reasons why your furnace pilot light may be failing:

Bad Or Worn Out Thermocouple - Causes of a Pilot Light That Will Not Stay Lit

We mentioned before that if your pilot light goes out, it might cause the gas to spread into the air and increase the chances of an explosion.

The thermocouple is one such device that takes measures to prevent a thing like this from happening. If there's no flame or pilot light, the thermocouple will generally signal the gas valve to close. 

However, if your thermocouple is old, worn out, or hasn't been working correctly, it might send the gas valve incorrect signals when the pilot flame is still on. This leads to the gas being cut off and the pilot flame disappearing. 

Solution:

In the case of a bad thermocouple, you might have to research and dig to pinpoint the root of your troubles. First, you should check whether your thermocouple is aligned above the spot where your pilot flame lights up. 

Since the thermocouple is a flame sensor, any misalignment would stop it from getting a correct read of the flame, and thus, a wrong signal would be sent to the gas valves.

This might happen because of sudden movements in your furnace that might have displaced the thermocouple. If this applies to you, make sure to fix the positioning and make sure that the screw holding the thermocouple is nice and tight. 

If there are no signs of misalignment and everything seems to be in order with the placement, your thermocouple may be due for a cleaning. A dirty thermocouple messes with the sensory functions and dulls them. And so, the sensor might not be able to detect the pilot light and cause the gas valve to shut off. 

Another aspect to explore concerning your thermocouple is whether it's simply bad at detecting heat. For this, you can use a multimeter to test the number of millivolts identified when you put heat near the flame sensor.

Usually, any heat should make your thermocouple run up to a millivolt range between 18 and 35. Still, if your thermocouple fails to reach even 18 millivolts, you should consider replacing the part, as it's simply inefficient. 

Dirty Furnace - Causes of a Pilot Light That Will Not Stay Lit

Bad maintenance is the leading factor behind the problems of many household appliances. This is especially true for dirt, which, when it builds up in one place, makes it hard for any unit to work. Similarly, if there's dirt in the orifice of the furnace, this might weaken the pilot flame. 

A weak pilot flame can quickly stop being lit. To detect signs of weak flame and dirt, note the flame's color. 

If your pilot flame is blue but tiny and inconsistent, or if your pilot flame is yellow or yellowish orange, it indicates a weak flame. Ideally, your pilot flame should be a clear, rich blue color, small but not small enough to disappear. 

Solution:

If it is a dirty orifice holding your pilot light flame back, you need to start cleaning. First, follow all safety precautions; turn off the gas valve, etc. You can clean your unit with the gas tube, through which you can blow some air. You can also clean the orifice by using a needle or something just as thin and small that can fit in the hole in the orifice through which the gas travels. 

If you're reluctant to get handsy with your pilot, it might be better for you to take the unit to a local parts or hardware servicing store that will clean it for you.

Service companies for furnaces will clean the whole unit, including the pilot, as part of their service. This can get pricey, but it's worth it for the smoothness, as well as the new furnace you'll be able to use afterward. 

Gas Regulator or Gas Line - Causes of a Pilot Light That Will Not Stay Lit

Gas goes into all the gas-powered appliances inside your home from the gas regulator, which is usually outside. If your gas regulator is broken or your gas line is bent, natural gas can't flow into your appliances as it should. 

In this case, you'll usually find that the flame on all your gas appliances, like the stove, the dryer, and the furnace, is weak and inconsistent because the lines aren't able to provide the units with a sufficient amount of gas. 

So, if you find all the gas-powered units in your home equally malfunctioning, take a trip outside to inspect the gas regulator or the gas lines. 

Solution:

If you are dealing with a problematic gas regulator or a bent gas line, this is a problem you should take to your local gas provider—and fast. If you've got no expertise in this area, it's going to be hard to diagnose whether the issue is serious or not. This is why it's advisable that you immediately seek out a professional. 

Wind Interfering with Pilot Flame - Causes of a Pilot Light That Will Not Stay Lit

This is one of the easiest and simplest causes of a pilot flame that won't stay lit. This is probably not the first thought that comes to mind because humans have a tendency to overcomplicate things at the slightest sign. A strong airflow could easily put out the flame since a pilot is usually small and easy to put out. However, they can stay lit for hours or even days. But we advise you to check your windows and doors and see if you're allowing any wind or breeze to flow through the gaps into your home. 

A strong airflow could easily put out the flame since a pilot is usually small and easy to put out. However, they can stay lit for hours or even days. By blowing out the pilot flame, you can make sure that a draft isn't finding its way in to make your warm afternoons uncomfortable.

Solution:

If a draft of wind from the window is ruining your perfectly good day, all you need to do is find the willpower to shut window and door openings and make sure there are no gaps allowing wind to enter your home and disturb the working of your furnace.

Safely Conducting Furnace Maintenance - Why Your Furnace Pilot Won’t Stay Lit

Before you do any work on your furnace, turn off the power switch and the circuit breaker. Make sure all electrical equipment is turned off before beginning any repairs.

A furnace should always be turned off before maintenance for a number of reasons, including:

  • If the furnace isn't switched off, it can release deadly sparks. These sparks have the capability of igniting furnace components and causing a fire.

  • A furnace needs to be turned off before usage because if it isn't, an emergency could occur and you wouldn't have time to flee. You won't be able to flee the furnace in time if there is a fire because of the heat and smoke.

  • Electric shocks can be very hazardous as well.

When the electricity is on, you shouldn't work on a furnace since the consequences could be fatal.

The interiors of furnaces can be dangerous, not to mention frequently unclean. A dust mask and goggles are the most important pieces of safety gear to wear when working inside a furnace. Also suggested are gloves, long trousers, and an arm-covering shirt.

Before undertaking furnace repair, make sure you have the appropriate tools.

If you don't have the right equipment or aren't confident you can handle the problem on your own, it's perfectly OK to ask for assistance. Contact a nearby HVAC company if you need help fixing your air conditioning system.

Conclusion - Why Your Furnace Pilot Won’t Stay Lit

Before exploring all these options, make sure you've also tried to relight your pilot light by yourself when it goes off. You'd have to push and hold a button that opens the valve. 

Then, light the pilot flame and wait for a few seconds until the thermocouple heats up. If the pilot light still doesn't stay lit after you let go of the button, it might be time for a general check-up of the furnace. 

A good furnace pilot light will ensure your furnace's safe and comfortable functioning. The above causes could go a long way in helping you figure out what is wrong with your furnace, and these solutions could fix that too!

Related Articles You May Like: