The Basic Steps to Adjust Your Pilot Light
Most gas fireplaces let you adjust the pilot light by turning a small screw or valve on the control box beneath or behind the fireplace. The screw is usually brass or steel and sits next to the pilot flame itself. Turn it clockwise to make the flame smaller, counterclockwise to make it larger. The adjustment takes seconds, but you need to see the flame while you turn it, so have a flashlight ready and work during daylight or with the room lights on.
Before you touch anything, turn off the fireplace and let it cool for at least five minutes. The control box gets hot. Locate the pilot adjustment screw — it is often labeled with a minus sign (smaller) and plus sign (larger), or marked "pilot" directly. If you cannot find it, check your owner's manual or look for a label on the control box itself. Some fireplaces have the screw on the front of the box; others hide it on the side or back.
Once you find the screw, turn the fireplace back on and light the pilot according to your normal procedure. Watch the flame as you make small quarter-turn adjustments. The pilot should be a steady blue flame about one to one-and-a-half inches tall. If it is yellow or orange, the flame is too small and needs more gas. If it is very large and unstable, turn the screw clockwise to reduce it.
Key Takeaways
- The pilot adjustment screw sits on the control box below or behind the fireplace and turns clockwise to shrink the flame and counterclockwise to enlarge it.
- A healthy pilot flame is steady, blue, and about one to one-and-a-half inches tall; yellow or orange color means the flame is too small.
- Always let the fireplace cool for five minutes before adjusting, and watch the flame while you turn the screw to see the change in real time.
- If you cannot locate the adjustment screw or the flame will not stay lit after adjustment, your control box may need professional service.
Why the Pilot Light Size Matters
A pilot flame that is too small will not heat the thermocouple — the safety sensor that tells the gas valve to stay open. When the thermocouple is cold, the valve shuts off and the pilot goes out. You will find yourself relighting it over and over. A flame that is too large wastes gas and can overheat the control box, shortening its life and sometimes triggering the safety shutoff.
The sweet spot is a flame that wraps around the thermocouple tip without engulfing it. Most thermocouples are a thin rod about two to three inches long, and the pilot should touch it but not completely surround it. If you are unsure whether your flame is the right size, take a photo with your phone and compare it to the diagram in your owner's manual.
What to Do If the Flame Will Not Stay Lit
If you have adjusted the pilot to a healthy size and it still goes out within minutes, the thermocouple itself may be failing. A thermocouple that no longer generates enough electrical signal will cause the gas valve to close, even if the flame looks fine. You can test this by relighting the pilot and holding down the manual gas knob for 30 seconds after ignition — if the flame dies the moment you release the knob, the thermocouple is likely bad.
A failing thermocouple cannot be adjusted back to life. It must be replaced. This is a job for a technician because it involves disconnecting the thermocouple from the control box and installing a new one. The part itself costs between $15 and $40, but labor will add to that. Before you call, make sure the pilot screw is actually in the right position — many people assume the thermocouple is dead when the pilot straightforward needs to be bigger.
Cleaning the Pilot Burner If Adjustment Does Not Work
Sometimes the pilot flame stays small no matter how far you turn the adjustment screw counterclockwise. This usually means the pilot burner opening is clogged with dust or debris. The burner is a small brass or steel fitting with a tiny hole, and even a speck of dust can restrict the gas flow.
To clean it, turn off the gas at the control knob and let the fireplace cool completely. Use a thin needle or a piece of wire — a straightened paperclip works — and gently poke the hole in the burner tip. Do not force it or enlarge the hole. A light touch is enough to dislodge dust. Blow gently into the hole or use a can of compressed air to clear any loose particles. Then relight the pilot and check the flame size again.
If the flame is still too small after cleaning, the burner itself may be damaged or the gas line to the pilot may have a partial blockage. At that point, a technician should inspect the line and burner assembly.
Understanding Your Control Box and Knob Positions
Most gas fireplaces have a control knob with three positions: Off, Pilot, and On. The Pilot position lets you light the pilot without opening the main burner valve. The On position heats the thermostat and opens the main burner when the room is cold. The adjustment screw controls only the pilot flame, not the main burner, so changing it will not affect how hot your fireplace gets when it is running at full heat.
Some newer fireplaces have electronic ignition instead of a standing pilot. These do not have a pilot flame at all — they light the main burner with a spark when you turn the knob to On. If your fireplace has no visible pilot flame, you have electronic ignition and there is no pilot screw to adjust. Check your manual to confirm which type you own.
When to Call a Professional
Adjust the pilot yourself if the flame is straightforward too large or too small and the screw turns freely. Call a technician if the screw is stuck or will not turn, if the flame will not light at all, if it lights but dies when ready, or if you smell gas near the control box. Gas leaks are serious and require professional attention.
You should also have a technician inspect the fireplace if you have adjusted the pilot multiple times and it keeps going out, or if the main burner will not light even though the pilot is healthy. These are signs of a thermocouple problem or a gas valve issue that is beyond adjustment.
Frequently Asked Questions
Which way do I turn the pilot screw to make the flame bigger?
Turn the screw counterclockwise to increase the pilot flame. Clockwise makes it smaller. If the screw is labeled with a plus and minus sign, the plus points toward larger and the minus toward smaller. A quarter turn at a time is enough — you will see the change when ready.
How do I know if my pilot flame is the right size?
The flame should be steady, blue, and about one to one-and-a-half inches tall. It should wrap around the thermocouple tip without completely engulfing it. If the flame is yellow or orange, it is too small. If it is very large and flickering, it is too big.
Can I adjust the pilot while the fireplace is running?
No. Turn off the fireplace and let the control box cool for at least five minutes before you touch the adjustment screw. The box gets hot enough to burn your hand. Light the pilot again after you have made your adjustment so you can see the new flame size.
What if the pilot screw will not turn?
Do not force it. A stuck screw can break, and forcing it may damage the control box. If the screw will not budge with gentle pressure, stop and call a technician. Trying to free it yourself can make the problem worse.
Is it normal for the pilot to go out sometimes?
No. A healthy pilot should stay lit continuously. If it goes out regularly, the flame is probably too small, the thermocouple is failing, or the burner is clogged. Adjust the screw first, then clean the burner. If it still goes out, have the thermocouple checked.