Gas Fireplace Repair – My Main Burner Flame Will Not Turn On

This section will help you diagnose and fix simple issues related to your main burner flame. If you do not see a pilot light in your fireplace please refer to the Pilot Light Troubleshooting page.  Also, if your main burner will run for a while, then go out, make sure your pilot stays lit.  If your pilot goes out as well you can refer to the Pilot Light Issues tutorial.

Main burner issues can only be four things:

  1. The wall switch is bad
  2. Your pilot flame is bad
  3. Your thermopile is bad
  4. Your main control valve is bad

Again, thankfully, all of these issues can be easily tested, and most of them can be fixed very easily.


Wall switch issues

The most simple of these issues, and consequently the most common, is a bad wall switch.  Every year I always get tons of service calls that are the result of a faulty wall switch. Again, this is probably the easiest thing to test and replace.

How does the wall switch affect the fireplace’s function?

Millivolt gas fireplaces have a pilot light that heats up a sensor (commonly called a thermocouple or thermopile).  The thermopile and thermocouple generates electricity when heat is applied to it (not much, actually under 1 volt).  This small amount of voltage is sent to the wall switch.  When you flip the switch on, it will send that voltage back to the fireplace and signal to the fireplace to turn on the flame.

What can happen over the years, is that the connections inside the switch can get dirty, corroded, or broken, causing a loss of this voltage at the switch.  So by the time the small amount of voltage gets sent back to the fireplace, it is not enough to signal the fireplace to turn on.

Testing the Wall switch

To test this, you will only need a screwdriver.  First you will want to find the wall switch that turns on the fireplace.  Again, this switch has less than 1 volt of electricity running through it, so there should be no issues with accidentally shocking yourself.  However, you will want to make sure that you have located the switch that turns on your flame, NOT your FAN or NOT for anything else such as a LIGHT SWITCH.   (You can always verify this after we take off the cover plate as just looking at the wiring should tell you what is what, but more on that later)

Next, we want to take our screwdriver and remove the cover plate:

Wall Switch cover plate

You should just need to remove the two screws on the face plate with a flat head screwdriver.

Next, we should double check the wiring to make sure we have the right wall switch.  We should just see two thin wires attached to the switch:


If it is a high voltage switch, we would see thicker wires and typically a ground wire like this:

Wall Switch Hot

If you are unsure, you can always turn off the circuit breaker for the room and make sure the power is turned off.  You can also purchase a voltage tester to find out if there is power present.

Next, we want to unscrew the next two screws that hold the switch itself onto the receptacle box:

Removing wall switch

Once they have been unscrewed enough you should be able to pull the switch right out of the box.  You want to be able to pull it out enough so that you can access the two wires on the side of the switch.

Now you’ll want to unscrew the screws that the wires are attached to.  Again, you only need to unscrew them enough to be able to pull the wires off.

Wires off wall switch

Once you have the wires removed from the wall switch itself, all we are going to do is touch the wires together.  This is basically just bypassing the wall switch and if the fireplace comes on, this should tell us right away that the old wall switch is bad.  If it is bad you should replace it with any single pole wall switch (you can buy these here or pick these up at any home improvement or hardware store).  You’ll probably want to bring the old wall switch with so that you can stick with the same color and that it will match with the rest of the house:


Wall Switch

If your fireplace still does not come on by bypassing the wall switch, the next step is what we call “jumping the valve”.  To do this, you will just need to take a wire (a paperclip works great) and complete the connecting between the TH and TP/TH terminals on the valve.

Place one end of the paperclip on the TH terminal and the other on the TP/TH terminal:

By doing this you are essentially bypassing the wall switch and any wall switch wiring, extra toggle switches, safety switches, and/or safety limit switches in the fireplace.  If the fireplace comes on when jumping the valve, you know that there must be something wrong with one or all of these items.

For additional ways to test your wall switch and/or wiring, here is a short video tutorial from that goes over this process:

Click Here for Part II: How to Test Your Pilot Flame