If your furnace isn’t heating properly, one of the first things to check is the pilot light. Many homeowners ask:
“How do I check a furnace pilot light?”
Even though newer systems use electronic ignition, many homes still rely on pilot lights. The good news is that learning how to check a furnace pilot light is simple and can help you quickly determine whether your system is working properly, or if it’s time to call for service.
Checking the Pilot Light Flame
The color of a suitable pilot light flame can vary, but it should be blue with a tint of yellow at the flame’s tip, regardless of whether your furnace runs on natural gas or propane. Rust or grime can also cause a bluish-green flame. The purpose of this inspection is to see if the standing pilot light is working properly.
The burner assembly and pilot should be visible after removing the furnace cover panel. You should be able to see the pilot light’s flame.
How to Relight a Furnace Pilot Light
Examine the color of the pilot light if it is lit. A suitable pilot flame should be blue with a yellow tip and strong enough to cover about 1/2 inch of the thermocouple tip.
The flame will be blue if it is too strong and improperly regulated, but it may be noisy and elevate the thermocouple, resulting in faulty furnace operation.
If the pilot light is turned on but the flame is a feeble yellow color, the thermocouple will not be heated to the correct temperature for the gas valve to open.
Replace the thermocouple if the pilot light does not illuminate or does not keep lit. When the cover is removed, look inside the furnace for any live power.
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WARNING Gas furnace repairs should be left to the professionals: Any unforeseen circumstances or concerns could swiftly escalate into a deadly situation. If you start working on your furnace and run into any problems, stop and call a professional. |
Adjusting and Controlling the Flame
The standing pilot flame is frequently adjusted with a tiny screw on the pilot valve body. To locate the screw, you may need to consult the furnace manufacturer’s instructions. To modify the flame throw, turn the screw as needed. You should search for the following flame anomalies:
Incomplete combustion and a lack of air generate a yellow flame. A dirty pilot tube tip may be to blame. With a little screwdriver or a nail point, you can generally clean this debris away.
The dirt inside the pilot tube causes a split flame. Clean the tube lightly with a needle or a little nail.
A draft is the most common cause of a flickering or wavering flame. Look around the room to see if there are any noticeable draughts. This flashing can be caused by the removal of the furnace’s cover panel, but it could also indicate a source of the continued draft that has to be addressed.
Frequently Asked Questions About Furnace Pilot Lights
What should a furnace pilot light look like?
A healthy pilot light should be blue with a small yellow tip and strong enough to cover the thermocouple.
Why is my pilot light yellow instead of blue?
A yellow flame can indicate incomplete combustion or a dirty pilot tube that may need cleaning.
What causes a pilot light to go out?
Common causes include drafts, a dirty thermocouple, or gas supply issues.
If your furnace pilot light won’t stay lit or doesn’t look right, it’s best to have a professional take a look.
At Martens Heating & Cooling, we help homeowners across the Fox Cities quickly diagnose furnace issues and get systems running safely again.