Gas Fireplace Wall Switch Not Working – Fixes + Troubleshooting

One of the most common problems that homeowners with gas fireplaces with wall switches often face is the main burner failing to light up even when the pilot flame is turned on. If you’ve come across this problem and are searching for solutions- you’ve landed at the right place. In this blog article, we’ll take you through how to troubleshoot and fix a faulty gas fireplace wall switch.

Why is my gas fireplace wall switch not working?

If the main burner on your fireplace won’t come on even when the pilot flame is on, it means that there’s an issue with your wall switch. So- why would a gas fireplace wall switch stop working? To answer this question, we’ll first explain how a gas hearth functions.

Once the pilot light is ignited, it heats up the thermocouple/thermopile sensor, which then generates small amounts of electric voltage (millivolts). This voltage is then routed to the wall switch. As you turn the switch to the ‘ON’ position, the same voltage is then sent back to the fireplace, signaling it to turn on the main burner.

Over the course of time, the wiring inside the switch may degrade due to corrosion, dirt build-up, and physical wear. This leads to the loss of electric voltage at the switch. When the switch is turned on, the diminished voltage that’s sent back to the hearth is not enough to trigger it to turn on the main burner flame.

How to Fix a Gas Fireplace Wall Switch that’s Not Working

A faulty wall switch is just but one of the issues that can cause the main burner flame on your fireplace to not come on. Other issues that might also cause fireplace failure include a faulty thermocouple/thermopile, a faulty pilot flame, and a faulty main control valve. Before you decide that your wall switch is the problem, you should check these other components and ensure that they’re not the cause of the gas fireplace failure.

Once you’ve ruled out all the other possible causes, it’s now time to troubleshoot the wall switch. To do this open the cover plate of the fireplace wall switch using a screwdriver. Most wall switches feature only two screws- one at the top of the cover plate and the other at the bottom- that can be easily removed using a flathead screwdriver.

Once you’ve removed the cover plate, double-check the wiring to ensure that it’s the right one. For a gas fireplace wall switch, you should be able to see two slender wires. Since the switch has less than one volt running through it, there’s no danger of electric shock.

It’s easy to differentiate fireplace wall switches (two, thin wires) from high-voltage switches connected to other electrical appliances, that usually feature three thick wires. If you’re still unsure- though- you can always turn off your main power supply as a safety precaution.

After you’ve removed the cover plate and checked the wiring to ensure that you’re indeed accessing the wall switch, unscrew the wall switch from the receptacle box. Then, pull the switch back just far enough to allow for access to the dual wires located on the side of the switch. Next, unscrew the wires from the wall switch and pull them off.

Once the wiring is free from the switch unit, bypass the wall switch by touching the two wires together. If the main burner flame of the fireplace turns on at this point, this should let you know that your wall switch is the issue. You can buy a replacement wall switch (single pole switch) at your local hardware outlet.

Meanwhile, if you’ve bypassed the wall switch and the fireplace burner is still not coming on, it’s likely that the issue probably lies in the wiring, additional toggle switches, fireplace safety switches, and safety limit switches. You can bypass all these components by connecting one end of a paperclip to the TH terminal of the valve and the other end to the TP/TH terminal. This troubleshooting method is referred to as ‘jumping the valve’. If your fireplace burner lights up after jumping the valve, then the problem lies in any of the above components and you’ll need to individually test them and replace the faulty one.

Heat n Glo wall switch not working

One of the most common issues reported by buyers of Heat n Glo fireplaces is the intermittent functioning of the wall switch. Sometimes, you’ll turn it on and the fireplace main burner will turn on. Sometimes- it won’t light up. The main cause of this issue is corrosion of the contacts inside the wall switch.

You can try to turn the switch on and off repeatedly to see if this will knock off the corrosion. A more effective fix would be to open the cover plate of the switch, unscrew the switch to access the wiring, and clean the wires and connectors using denatured alcohol and steel wool. This should knock off the corrosion and prevent loss of millivolts.

Lennox Fireplace wall switch Troubleshooting

If you have a gas fireplace from the Lennox brand and you suspect that the main flame is not turning on due to wall switch failure, we recommend inspecting the wiring that connects to the wall switch. Faulty wires are usually the most common problem in Lennox fireplaces with a wall switch. Loose wires will prevent the fireplace from turning on when the wall switch is flipped on or during thermostat calls, as the voltage is too low.

Since we’re dealing with millivolts, any significant loss of voltage and the gas valve will fail to open. To determine whether the loss of voltage is due to loose connections on the wall switch, measure the voltage on the TP and TP + TH terminals. This will give you the voltage directly generated by the thermopile. Then, measure the voltage across the TP and TH terminals.

If this second reading is less than the thermopile voltage, it means that there’s a short on the wall switch due to loose wire connections and the voltage is too low to trigger the opening of the gas valve. However, if the reading on the thermopile is below 200mV, it means that the problem doesn’t lie in the wall switch, but in the pilot flame.  A dirty pilot orifice will result in a low pilot flame that can’t adequately heat up the sensor to create the required amount of voltage.

Fortunately, Lennox offers free fireplace maintenance and repair services under their product warranty covers. You can- therefore- contact them to send a technician to correct any wall switch wiring problems- or issues related to dirty/clogged pilot orifice.

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