Gas Fireplace Control Valve Troubleshooting: Simple Guide and Solutions

Gas fireplaces have recently replaced the traditional fireplaces as a means for more convenience and ease of use. But each of them has its own issues. A very common issue with gas fireplaces is that they often have malfunctioning control valves, which require troubleshooting from time to time.

When trying to light up a fireplace, the most common issue is that the flame does not want to light up. This is often a problem with the control valve which requires gas fireplace control valve troubleshooting.

Some of the typical problems and causes of a gas fireplace control valve troubleshooting are discussed below.

ProblemPossible Cause
Pilot flame too shortFaulty adjustment screw
Pilot flame does not heat the thermocoupleWrong direction of pilot hood and flame
Faulty connection between the thermocouple and valveDirty threads of the connecting nut
Pilot flame does not stay litFaulty gas supply, low voltage
Pilot flame ignites, but fireplace does not turn onLow voltage, poor connection
Heating issuesThermostat malfunction

Problems Regarding Valves with Thermocouple Only

Pilot Flame Too Short

The length of the pilot flame can be adjusted by a knob connected to a valve to control the gas supplied to it. Many of these valves controls also have an adjustment screw to adjust the pilot flame.

A pilot that is too short may allow the pilot to stay lit after ignition, but may not create enough heat to allow the burner to ignite. This is often an issue with a damaged screw or a dirty one.

A damaged screw must be replaced with a new one. The gas fireplace control valve troubleshooting for such a problem is simple and does not require the help of a professional.

How To Replace An Adjustment Screw?

  1. The first step is to completely turn off your fireplace. Both the electricity and gas.
  2. Let it cool down completely.
  3. Remove the screw with a screwdriver with matching head.
  4. Obtain a new screw either from online or from a retail store, or clean the old one if it is dirty.
  5. Screw the new/clean screw back into place.
  6. Turn on the fireplace and try readjusting adjusting the flame.

Pilot Flame Does Not Heat the Thermocouple

The way this mechanism works is that, the pilot flame heats up the thermocouple, which after reaching a certain temperature, triggers the valve to light up the fireplace. If the pilot flame doesn’t light up the thermocouple, it is mostly always an issue with the direction of the flame or the pilot hood.

If the flame strikes the thermocouple at an angle that is too low, the device may shut down or fail to generate enough millivolts to operate the valve.

Soot should be removed from the pilot hood and aperture to prevent the pilot flame from being obstructed.

How to Replace an Adjustment Screw?

  1. Completely turn off the fireplace and let it cool down.
  2. Open the glass door.
  3. Remove the pilot hood by simply pulling it off.
  4. Clean the pilot hood with a cloth or brush of any soot that is on it.
  5. Slightly bend the hood towards the flame if the angle is too shallow, but practice caution while doing so.

Faulty Connection Between the Thermocouple and Valve

Often times a faulty connection between the thermocouple and valve might lead to the fireplace not starting up. It’s mostly caused by the dirty threads of a connecting nut.

A dirty nut can be easily cleaned by using a pencil eraser and re-tightening it afterwards.

Thermocouple & Thermopile Valve Problems

For fireplaces with a thermopile along with a thermocouple, if the pilot lights up and stays lighted after the knob is turned off, the issue is most likely with the thermopile side of the valve. Let’s take a look.

Pilot Flame Does Not Stay Lit

Check that the gas to the appliance is turned on and that the valve is in the right (pilot) position and completely depressed when lighting. If the pilot does not light or stay lighted after the knob is released, the thermocouple is not providing enough power for the valve.

If the pilot burns but does not stay lighted when the knob is released. It’s possible that the thermocouple needs to be changed. This is a fix that is best left up to the professionals.

On the other hand, the thermocouple may not be properly heated by the pilot flame, or there may be soot or another obstruction in the pilot tube, orifice, or hood, causing the pilot to shrink.

How To Prevent Excess Soot?

  1. Adjust the log set so that the flame does not come into contact with it too much.
  2. Ascertain that the set point is appropriate for the appliance/gas type. It may be necessary to raise the shutter opening if your machine has adjustable shutters.
  3. Examine the burner’s aperture at the base. This opening should not be filled with anything.

Pilot Flame Ignites but Does Not Stay Lit

Oftentimes, the appliance will not turn on even after the pilot being lit. This is caused by the low voltage produced by the thermopile and requires gas fireplace control valve troubleshooting.

How to Fix the Voltage Issue of a Thermopile?

  1. Check the produced voltage using a volt meter.
  2. If it’s not enough to power on the control circuit, it can be easily adjusted with the pilot screw.

If the thermopile is producing enough voltage, the issue lies with a faulty or poor connection which requires a skilled electrician to fix.

Valve Problems Due to Electronics

Heating Issues

Inside the fireplace is a thermostat that controls the heat by regulating the flames. If the thermostat is damaged, the fireplace may provide too much or too little heat.

Replacing the thermostat requires the help of a professional unless you have enough experience as an electrician.


Traditional fireplaces have long been replaced by gas fireplaces, for their ease of access, easy maintenance and convenience. But gas fireplaces have their own fair share of problems which often lie with the control valve.

Hence, gas fireplace control valve troubleshooting is pretty common among users who’ve installed them. In this guide we’ve discussed various problems, their causes, and how you might solve them.

I hope this guide will help you solve any issue you might face with the control valve of your gas fireplace.

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