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5 Reasons Gas Fireplaces Won’t Light (& How to Fix It)

We’re staying with some family and their gas fireplace won’t light. Winter is approaching fast, so I did some research to help them out. Here’s what I found.

Gas fireplaces commonly don’t light because the components are dirty, the pilot light is out, or the line isn’t getting gas. Less common reasons are dead batteries in the remote, a broken wall switch, or a broken thermocouple. When troubleshooting, start with the switch and follow your way up the fireplace.

Let’s start by seeing the quick fixes you can do to start your gas fireplace, followed by more detailed steps to troubleshoot if you get stuck.

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1. Dirty Components

cleaning a gas fireplace components
Cleaning the thermocouple on a gas fireplace.

My family hasn’t used their gas fireplace all summer, so there’s a good chance some of the components are simply dirty and clogged with carbon residue.

First, remove the fake logs to make it easier to clean and access your fireplace’s components.

When cleaning your gas fireplace, use a wire brush and clean off the carbon from:

  • Pilot Light
  • Gas Openings
  • Thermocouple
  • Thermopile Leads
Image source: airconditioningarizona.com

You can also use a vacuum to clean the loose debris, but a wire brush works better as the carbon residue is tough to get off.

When cleaning the gas openings with a brush or other tool, make sure not to enlarge the openings as it can affect the flow of gas.

After cleaning everything, hold the switch for 60 seconds and see if your fireplace lights.

If you don’t hear clicking, there’s likely a problem with your pilot light.

If you do hear clicking and your fireplace still won’t light, there could be an issue with the gas intake.

2. The Pilot Light is Out

turning on the pilot light on a gas fireplace

Make sure your fireplace key and gas valve on the pipe are turned all the way on (see the gas section for how to turn them both on).

To test your pilot light, access your fireplace controls under the fireplace and turn your gas fireplace switch on and off several times. There’s a chance it’ll light.

If it doesn’t light, turn on the switch for 60 seconds and see if you get an ignition (this is a common fix).

Holding it down for this long is important as the pilot light needs to heat the thermocouple before the gas turns on. You can also use a lighter to heat the thermocouple.

Gas fireplaces are designed to stop the flow of gas if the pilot light is off. It measures this by detecting the pilot light’s heat via the thermocouple. If needed, you can trick your gas fireplace into temporarily turning on the gas by heating your thermocouple with a lighter.

I included an image of the thermocouple in the above section, but you’ll see it as a small cylinder next to the pilot light.

Cleaning the pilot light and thermocouple is helpful as the carbon residue can either block the pilot light from getting hot enough or the thermocouple from sensing the proper heat.

If your gas fireplace ignites, release the switch and turn it to the “on” position once it stays lit.

If your pilot light does turn on, but your gas fireplace still isn’t igniting, check the gas line next.

3. Remote Control or Wall Switch is Dead

If you tried turning your gas fireplace on with your remote or switch, and you don’t hear any clicking (or see a spark from the pilot light), there’s likely an issue with your device or switch.

Remote Control

remote control for a fireplace

For remote controls, first check the batteries are new. Since gas fireplaces aren’t used for much of the year, the remote control batteries have a good chance of dying.

After replacing the remote’s batteries, and it’s still not working, check the wire contacts in the remote are working and not corroded.

If you do see corrosion, clean it off using a bit of vinegar and baking soda.

When cleaning, be careful not to get liquid inside the rest of the remote as it can damage its internal components.

Try using the remote again. If your gas fireplace still isn’t lighting, try using the manual switch next to the fireplace’s burner instead. If that works, you likely need a new remote.

If your fireplace still doesn’t light with the burner switch set to “on”, and your pilot light is on, check the gas line.

Wall Switch

a wall switch

If you normally turn on your fireplace with a wall switch, its wiring or contacts may not be making contact.

While the wall switches are low voltage and can be handled, if you’re uncomfortable with handling wires, hire a professional to check your fireplace and wiring.

To test this, start by unscrewing and removing the outlet cover to expose the wires.

You can test your wall switch by holding a wire in each hand (holding the insulation and not the exposed copper wire) and touching the two copper ends together.

If your fireplace lights, it’s a bad wall switch and it needs to be replaced.

You can test if your gas fireplace is working by using the switch located next to the burner. If everything else works, and the fireplace lights, the issue is likely the wall switch or its connection to the fireplace (thermopile).

If your fireplace doesn’t light from connecting the wall switch’s cables, follow the cables to the fireplace and test the connections along the way (starting with the thermopile leads and working your way up the chain).

4. No Gas

our fireplace key
Our fireplace key.

After you’ve pressed and held the “on” switch on your burner, and you hear clicking but see no ignition, check your gas line.

Here’s a quick summary of the steps to follow when checking your fireplace’s gas intake:

  1. Turn your fireplace key on
  2. Listen for any gas
  3. Check your gas line is on
  4. Try using a lighter

Start by turning your fireplace key on (counterclockwise).

You can usually find this near your fireplace (ours is on the floor next to the fireplace), but sometimes it’s found in the laundry room or other nearby room.

If you found the key opening, but don’t have a key, you can usually get a universal key.

After turning your fireplace key, listen for any gas entering your fireplace (you may have to remove your fireplace glass door before you can hear it, see below).

removing the glass door on a gas fireplace

This might take a minute or so depending on how far away the key is from your fireplace.

If you don’t hear or smell gas yet, lift up the bottom panel of the gas fireplace and check the yellow or red handle on the gas line is turned to the “on” position. You can tell if it’s on if the handle is parallel with the gas pipe.

If the handle is perpendicular or at a 90º angle, it’s currently off and needs to be turned on.

If your pilot light is out, the thermocouple won’t turn on the gas. Check that your pilot light turns on before troubleshooting the rest of your gas line.

Try listening or smelling for the gas again, and use your fireplace switch again to ignite the gas.

If you’re getting gas, but no light yet, try using a lighter to ignite the gas opening. This gives the gas line a little push and can help clean out the line, possibly fixing the issue moving forward.

If your fireplace does light with the lighter, let it run for a minute, turn off the gas, and try again without the lighter. If it works, your issue is likely fixed.

5. Thermocouple is Broken

thermocouple on a gas fireplace

A broken thermocouple is possible, but not likely. If your pilot light is turning on but you’re not getting gas, and you’ve checked everything else, consider replacing your thermocouple.

A thermocouple allows the gas line to open once it’s heated up enough. Normally, the pilot light is enough to heat it, but debris can block and affect the pilot light’s flame.

Pilot lights should have a blue flame. If it has an orange flame, there’s likely carbon residue blocking it from burning properly.

If you’ve cleaned your pilot light, and believe it’s not heating the thermocouple sufficiently, test your thermocouple by using a lighter to heat it up. This can take up to a minute.

There’s also a chance your thermocouple is working properly, but there’s a blockage in the gas openings. If you haven’t already, use a wire brush to clean the openings.

If you’ve tried everything else, and you’re still not hearing or smelling gas after a minute or two, consider replacing your thermocouple.

Bonus Steps to Troubleshoot a Gas Fireplace

If the above steps didn’t work for you, here’s a slightly different approach that works for many people:

  1. Check that your pilot light turns on. Clean any debris from the pilot hood and bypass the remote or wall switch, turning the fireplace on using the controls underneath the fireplace. If the fireplace lights, turn it off and try using your remote or switch.
  2. Try your remote or wall switch. If they aren’t working, check the remote’s batteries and contacts, or the wall switch’s contacts. If the wall switch’s contacts don’t ignite the fireplace, check the thermopile cable leads.
  3. Test the thermopile by testing the 2 terminals the wires are attached to (labeled “TH” and “TPTH”). Since they’re low voltage, connect the 2 terminals with a paper clip. If it works, it’s likely the wall switch or its cable.
  4. Further test the thermopile by using a multimeter (set to DC and 2000 millivolts). With the multimeter, touch the “TP” and “TPTH” screw-heads. It should have one white and one red cable. The multimeter should read at least 325. If it’s under, the thermopile needs to be replaced.
  5. Use a vacuum to clean the pilot hood. After cleaning, use the multimeter to test your thermopile and see if the reading climbs above 325.

For more details on how to test your fireplace’s thermopile, check out this post by mygasfireplacerepair.com

If you’d like a visual of the above troubleshooting steps, check out this video by Mike Klimek.

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