Skip to Content

Why Do Gas Fireplaces Go Out?

One of the primary reasons for a gas fireplace going out is dust or soot buildup in the pilot light, the thermocouple, the thermopile, or the Oxypilot. Other reasons might include a faulty thermocouple or thermopile, incorrect gas service pressure, a faulty gas valve, moisture in the gas line, or faulty wiring.

Dust in the pilot light can cause what is called a “lazy flame” that doesn’t produce enough heat to trigger the thermocouple to keep the gas going. The thermocouple is a metal sensor heated by the pilot light. If it gets enough heat to know the pilot light is on, it will allow the gas to pass through the system and burn throughout the fireplace. 

For more information on what a thermocouple or thermopile is, check out this site.

The Oxypilot is designed to monitor the oxygen in the room and turn off the gas for the fireplace if the oxygen levels drop too low. Dust or soot in this system blocks the sensor from reading accurate oxygen levels and will automatically turn off the gas. This brings up the question: Would a gas fireplace stay on without any problems?

Looking to become more self-sufficient? Join me and 14,000 others on Abundance Plus and get discounts, masterclasses, community, and more.

Do Gas Fireplaces Normally Stay On?

a lit gas fireplace

Gas fireplaces should be able to run all day long if there are no malfunctions, dust, or faulty parts. There are plenty of parts in gas fireplaces that may need to be serviced or replaced if the fireplace isn’t working properly, but a smoothly running fireplace would need to be manually turned off unless you have a system on a timer. Just because a gas fireplace can stay on for as long as you want doesn’t always mean it should.

Ventless gas fireplaces should only run for about three hours at a time. After three hours, you run a higher risk of using up the oxygen in the room. Vented gas fireplaces can run for much longer, but it is still highly recommended that you do not sleep with them running. Also, it is recommended that you have a high-quality carbon monoxide monitor in the same room as the fireplace. This article explains some of the safety guidelines for owning different types of gas fireplaces.

One thing that can be left on at all times is the pilot light. Some people leave their pilot light on year-round, while some shut it off during the off-season. There are pros and cons to both. Pros of keeping the pilot light on are that you can turn your fireplace on at any point with the flip of a switch instead of having to go and relight the pilot light. You also have less need to get it serviced because there is less opportunity for dust and cobweb buildup in the pilot light area. Cons are that it will cost more to have your gas running all year and a white film can form over the glass doors of the fireplace from sulfur residue. 

So the pilot light can be left on once you get it working, but what do you do if you can’t turn it on?

How to Fix a Gas Fireplace That Won’t Stay On

The first step in fixing a broken gas fireplace is determining where the problem is. You should first check if the problem is with the pilot light or with the thermocouple/thermopile. 

Start the fire and keep the pilot light on for a few minutes. If everything is working normally, the fire should start up when you switch the pilot light on. A healthy pilot light should range from sky blue to dark blue and should be aimed at the thermocouple.

If the pilot light stayed on through the above process but the fire wouldn’t start, then the problem is with the thermocouple or the thermopile. If the pilot light wouldn’t stay on, then the problem is with the pilot light.

If the problem is with the thermopile:

  1. You will need to check the output of the thermopile using a multimeter. Start by running the pilot light for more than two minutes, then turn the fireplace off so you can get to the thermopile. 
  2. Find the main gas control valve, follow it to the thermopile sensor, and from there, locate the Electric Contacts that should be labeled TH/TP and TP.
  3. Place the multimeter on these terminals and take a reading.
  4. If it reads less than 300 millivolts, then the thermopile will need to be cleaned or replaced. 
  5. To clean the thermopile, scrub the soot off with a stainless steel brush and/or fine-grit sandpaper. Do not use chemicals. This could cause unintended reactions.
  6. Test with the multimeter again. If it still reads under 300 millivolts, the part will need to be replaced. 
  7. Check the thermocouple with the multimeter as well to see if it is over 25 millivolts. If not, attempt to clean it in the same way as the thermopile or replace the thermocouple as well if cleaning doesn’t improve the voltage.

If the problem is with the pilot light:

  1. Check for and clean out dust in the hole on the brass tail or the connector between the pilot supply and the pilot burner. 
  2. Use a straw or canned air to blow down through each pilot hole.

Unfortunately, more complicated problems with the pilot light are not so easy to fix. If any gas supplies or fittings need disconnected or any parts need to be changed, it is best to call a technician to help. They will have to check the entire unit and could end up replacing parts, but they have specialized knowledge and more experience dealing with these problems. When dealing with gas lines and fire, it is usually better to be safe than sorry. A mistake that results in breaking the glass doors of your fireplace would be just as (or even more) costly as calling a technician to do a full service.

If none of these solutions have helped or the problem is something outside this list, it’s probably time to call a technician. 

What to Do if Your Gas Fireplace is Turning Itself On

If your gas fireplace is turning itself on unwarranted, the first assumption might be something supernatural like ghosts. In reality, it is probably a mechanical malfunction. There are a few reasons why your gas fireplace might be turning itself on. One is that the thermopile or thermocouple has shorted out, causing the fireplace to shut down or turn back on at random. Another reason could be that the remote control receiver is malfunctioning. And one more reason might be that the wiring has shorted out. 

To fix the problem with the remote control receiver, the receiver will need to be disconnected, or you will need to turn the fireplace to manual mode. It may not be as convenient if you have a remote-controlled fireplace to operate it manually, but it is better than letting the fireplace control itself. For the problem with the wiring and the thermocouple/thermopile, the best suggestion if you don’t have electrical experience would be to get the fireplace serviced. Once again, it is much cheaper to have it done by a professional than to try to repair damage if the home fix was not done right. 

Check out this YouTube video below for a tutorial on how to test a thermocouple. It also explains what some of the parts look like and what you should be checking for. 

Need More Help?

You can always ask us here at Fireplace Tips, but you should know the other resources available to you! Here are the resources we recommend.

  • Chimney Safety Institute of North America (CSIA): The CSIA is your BEST resource for fireplace and chimney safety at home. They’re a non-profit governed by a volunteer board of directors dedicated to the education, training, and certification of chimney and industry related professionals.
  • Self-Sufficiency and Off-Grid: If you’re like me and passionate about off-grid and self-sufficiency, see my number 1 resource—Abundance Plus. Check out their Frugal Homesteading Course on growing 90% of your own food. Get 7-days free and 10% off with the code: TYLER10