If you can’t get your furnace to light, it could be that the pilot light is out or the igniter isn’t working. Standing pilot lights aren’t all that common in furnaces anymore, but some people do still have older units that use this form of ignition. If so, here is a full overview of how to relight your furnace’s pilot light and also the issues that can prevent the pilot from lighting or staying lit.

How to Know If Your Furnace Has a Pilot Light

The majority of gas furnaces no longer use a standing pilot light. Instead, they typically use either an intermittent pilot or some other type of electronic igniter. The reason is that standing pilot lights waste quite a bit of energy since some gas is always flowing to ensure that the flame stays lit.

An intermittent pilot works similarly to a standing pilot light in that it uses a flame to ignite the gas flowing into the furnace. The difference is that an intermittent pilot doesn’t have a constant flame and instead only lights when the furnace first needs to start heating.

Some furnaces also use a direct-spark igniter. Instead of a flame, this type of igniter uses electricity to produce a spark that ignites the gas flowing into the furnace. You can also find furnaces that use a hot-surface igniter, which is somewhat like a lightbulb filament. Electricity flows into a metal probe and almost instantly makes it hot enough for it to ignite the gas.

If you have an old, low-efficiency furnace, there is a chance that it does have a standing pilot light. This is something you can easily check by looking at your furnace to see if you see a constant flame even when it is not currently running. You can also open the access door to look for a pilot control knob.

If you don’t see a control knob or a flame, it means that your furnace doesn’t have a standing pilot light. If your furnace doesn’t have a pilot light and you can’t get it to turn on, you will need to have the electronic igniter and the rest of the furnace inspected to determine why it isn’t lighting.

How to Ignite a Pilot Light

If your furnace does have a standing pilot light, relighting it is usually a simple task. After locating the pilot control knob, you will first want to adjust it to the “OFF” position and then wait for five to 10 minutes before you try to relight it to make sure that there is no residual gas in the unit. You can then turn the knob to the “Pilot” position and press the knob in as far as it will go. Once the knob is depressed, you should smell and potentially hear gas flowing to the pilot.

Keeping the knob pressed in, use your opposite hand to press the igniter button until you see that the pilot flame is lit. If you don’t see a spark when you press the igniter button or you can’t get the pilot to light, you can try to manually light it with a match or stick lighter.

Once you see the pilot flame, you will need to continue to hold the control knob in for around 30 seconds. This ensures that the thermocouple that detects the pilot flame has enough time to heat up. If you release the knob too soon, the thermocouple won’t properly detect the heat from the flame and the pilot will instantly go out. This occurs because the thermocouple is what controls the flow of gas to the pilot. If it doesn’t detect the flame, it will close a valve and shut off the gas flow as a safety precaution.

If the pilot stays lit when you release the knob, the last step is to turn the knob to the “ON” position. If the flame goes out when you release the knob, you will need to turn the knob back to the “OFF” position and again wait for five to 10 minutes before trying to relight it. If you still can’t get the pilot to stay lit or it won’t ignite at all, it likely means that there is an issue with the thermocouple, pilot gas tube, or pilot control.

Thermocouple Issues

The most common reason that a pilot light won’t stay lit is that the thermocouple is not detecting the heat from the flame for some reason. The thermocouple is temperature sensitive and contains a small electric current. Heat activates the thermocouple and causes it to send an electric signal to keep the gas valve open. If it doesn’t detect the heat and send this signal, the gas valve will close the instant that you release the pilot control knob.

This can easily happen if the thermocouple gets bent as its probe needs to come into direct contact with the flame to work correctly. You should see a thin metal probe when you look closely at the pilot light, and this is the thermocouple. If you see that the probe doesn’t come into contact with the flame when you try to light the pilot, you can try to very carefully bend it back so that it is in the center of the pilot light. If you do attempt this on your own, you need to be extremely gentle as you could easily break the thermocouple and cause it to need to be replaced.

Thermocouples can also stop working because they become covered in grime and dirt. Anything coating the thermocouple can insulate it so that it can’t detect the heat from the flame. The solution to this issue is to gently clean the thermocouple with sandpaper. Due to the potential of breaking the thermocouple, we usually wouldn’t recommend doing this on your own.

There is also a chance that the thermocouple has failed and no longer carries the electrical current it needs to keep the gas valve open. Should this happen, the only solution is to have the thermocouple replaced. This can be tested by having a furnace technician use a multimeter to measure whether there is a current flowing through the thermocouple. If there is no current, it means the thermocouple is broken and needs replacing.

Gas Flow Issues

If no gas is flowing to the pilot light, you obviously won’t be able to get it to light. This can happen because the furnace’s main gas valve isn’t fully open or if your gas supply is shut off or interrupted. There is also a chance that the pilot tube that supplies gas to the flame is clogged. This can be checked by using a needle to try and clean out any debris from the tube and then attempting to relight the pilot.

Faulty Pilot Control

The pilot control itself can also fail due to age or wear and tear, and this will also prevent it from lighting. This is also something that a furnace technician can easily check. Replacing the pilot control is slightly more expensive and time-consuming than fixing a thermocouple issue, but it is still much better than having to buy a new furnace.

If you’re having any issues with your furnace’s pilot light, the technicians at Specialty Heating & Cooling LLC are ready to help. We maintain and repair all types of furnaces, and we also specialize in furnace installation. Our technicians also install and service air conditioners, ductless mini-splits, heat pumps, air purifiers, and water heaters. If you need a furnace inspection or any other residential or commercial HVAC service in the Tigard area, give Specialty Heating & Cooling LLC a call today.

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