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We can all say that the toggle switch you use to turn on the fireplace is a lifesaver, right? And when these go out, it can be extremely frustrating. I have worked on countless switches over the years and have found a few reasons why they go bad. In this post, I have gone through the most frequent problems with gas fireplace wall switches and how to troubleshoot each one. I’ve also disclosed a few alternatives to using these switches.
While the switch runs a test drive with the pilot valve, it can sometimes act up and not fire. There might also be issues like inconsistent functions, auto shut-offs, and, god forbid- the switch can just be bad.
Gas Fireplace Wall Switch: What, Why & How
I’ll start with the basics for those new to the world of gas fireplaces.
The question of the moment is- what does the wall switch do for a gas fireplace?
Simply put, a fireplace wall switch is a toggle switch that opens or closes the circuit between the thermopile and the gas valve. It operates at millivolts, meaning it can operate at very low-voltage electricity(350-1000 millivolts).
Why is it used? Well, it’s a safety feature that prevents the gas valve from turning on if the pilot light is not working properly.
How Does A Gas Fireplace Switch Work?
To understand its function more, we need to step back and understand how the wall switch works with the thermopile, pilot light, and gas valve.
The image shows that the pilot light is heating up the thermopile. Thermopile is designed to generate about ½ Volt(500-750 millivolt) of electricity if it’s heated for about 2 minutes. The pilot light, a small flame, delivers this heat.
Once the wall switch is closed, the electricity goes from the thermopile to the gas valve and turns the gas valve on. If you don’t close the switch, the gas valve won’t open, and the fireplace won’t turn on.
Done with the basics? Let’s examine why gas fireplace wall switches might not work and their solutions.
3 Ways How to Fix A Gas Fireplace Switch
There are 3 ways you can fix a gas fireplace wall switch. And it depends on the issues within it that will let you know which path to take to fix it.
Problem 1: The switch might just be bad. You would then have to replace the millivolt switch with a fresh one.
Problem 2: The wiring might be bad or corroded. Replacing the wiring is the solution.
Problem 3: Enough voltage might not be provided to the switch. The solution can be either to clean up the wire or the control valve of the gas.
That’s the simplified version of the most common problems. In the next section, I’ll dive into each problem more and offer some solutions you can implement on your own.
Problem 1 of 3: The Switch Has Gone Bad
Let’s start with the obvious: troubleshooting to check whether the switch has gone bad.
Fireplace wall switches are pretty low-key and might go bad quickly. If so, it won’t let you turn on the fireplace. Because if the circuit behind the wall switch isn’t closed, the pilot light won’t send a ‘green’ signal to the gas valve. Therefore, the fireplace won’t work at all.
How Would You Know if the Switch is Bad?
To know if the fireplace wall switch has gone bad, you need to bypass the switch and check. A’ faulty’ switch is confirmed if the circuits are closed and the thermopile works well!
Here’s a step-by-step guide to doing that:
- Remove the cover plate from the wall switch by unscrewing the flat screws. Use a screwdriver.
- If there are another couple of screws(flat screw 2) holding the switch itself(not the cover) to the wall, unscrew them as well. Done so, the switch will pop out.
- Once the switch pops out, double-check if it’s the fireplace wall switch or not. The wires connected to it will be thinner than usual electric ones(your fan, light, etc). If not, you’ve mistaken the fireplace switch for something else.
- Remove the wire from the switch by unscrewing the terminal screws that hold the wires to the switch.
- Now, touch the wires together and twist them a few times. This is to ensure the switch is bypassed and the circuit is closed.
- Try turning on the fireplace with the pilot light and ignition switch. If it works, then your wall switch is gone.
Solution: Replace The Millivolt Switch
Yeah, you heard it right. Replacing the fireplace switch is the ‘almost’ only option here. These are called millivolt switches, which are pretty different from typical wall switches.
The next question you might be thinking of is- what is a millivolt switch?
Millivolt switches are designed to work on millivolt circuits like gas fireplaces, unlike regular 120V wall switches. You’ll notice the wires connecting to a fireplace switch are thicker than other electric appliance wires. And the low operating voltage is the reason.
Here are some of the millivolt switches that work great with gas fireplace circuits-
- Decorative rocker-style wall switch and cover plate
- UL listed switch
- 20’ 18-2 low-voltage wire included
- 4 Button Wired Timer with 30/60/120/OFF minutes
- Battery Operated
- Surface Mounted
- Country of origin: United States
- Wireless wall mounted single function On/Off operation
- All battery operated-R.F. with 65,536 security codes
- Battery powered receiver box with learn function and On/Remote/Off slider switch
- Receiver can be installed in wall, on the hearth or under the fireplace behind the control access panel
- Includes transmitter, receiver, wall clip, wall plate, installation instructions, batteries
|Skytech Wall Switch for Fireplace||Real Fyre WS-1|
|– Comes with 20 feet 18-2 wire|
– Replacement for stock fireplace switch
| – Comes with 15 feet 18 gauge wire|
– Doesn’t include the cover plate
|Check Price||Check Price|
How To Replace a Millivolt Switch
Below, I’ll explain the steps of replacing the fireplace switch with a new one-
- Turn off the pilot and ignition switches from the fireplace control panel.
- Find the right location for the switch to install. Ensure you don’t have to use a wire longer than 15 feet to reach the switch from the gas valve. If you’re replacing the switch with pre-installed wiring, skip the step.
- Unscrew the terminal screws(that hold the wires).
- Connect the wire leads to the metal terminal screw and tighten the screws. Connecting a spade terminal is good, as they offer a secure connection. If not, twist the end of the wires and place them into the terminal screws.
- Put the switch back to the wall and connect both set flat screws(one for the switch frame and another for the switch cover).
- Sometimes, the home builder might right the wall switch to your fireplace. In that case, changing it with the right millivolt switch is the only fix.
- To replace a switch with a new one, ensure the dimensions, colors, and, mostly, the screw positions are the same.
Problem 2 of 3: The Wiring Has Issues(Loose or Gone Bad)
From the previous problem, if you have not found the fireplace switch to be bad, it’s time to check whether the wire is troubled. It can either be a loosen-up wire lead or a damaged wire. We’ll cover both in the following section.
How Would You Detect a Loose Wire?
To detect a loose wire, the steps are pretty simple-
- Unscrew the switch cover plate(flat screw set 1) and the switch itself(flat screw set 2) with a flat screwdriver.
- Check for a loose wire connection on the terminals.
- Tighten the connections and check back if the fireplace works or not.
- Redo the flat screws and put the wall switch back in its place.
That’s it! No further fix is required.
But if the wire is faulty, then it’s a whole different and harder process. You need to bypass the wire on the gas valve. Here are the steps of doing it-
- Open the control panel of your gas valve.
- Locate two terminals called ‘TH’ and ‘TP’.
- Take a jumper wire, a paper clip, or a small insulated wire. Put the bare ends of it to the terminals from the previous step.
- Try turning on the fireplace as usual. If it works, then a bad wire is confirmed.
If you can detect a bad wire this way, the next step is to replace the wiring.
Solution: Replace The Wiring
Now it’s time to get rid of the bad wire and install a new one.
Before we start, here is a simplified wiring diagram of a gas fireplace to help you get an image of what you’re dealing with-
See the black arrows out there? These are the wires we’re going to replace in a few moments. We’ve explained how the system works. So not going to waste any more of your time here.
Note that the fireplace wall switch must be connected with 18 AWG, nothing more. Here’s a list of wires we recommend to buy if you haven’t already-
- 16.4 feet long: CBAZY Hook up Wire Kit
- 10 feet long: TUOFENG 18 AWG Electrical Wire
- 40 feet long(in case of two installations): TYUMEN 40FT 18 Gauge Wire
Collected the wire? Cool. Here go the steps of replacing bad wiring of a gas fireplace switch-
- Make sure two ends of the wire are securely connected to the ‘TH’ and ‘TP’ terminals on the fireplace control valve.
- Run the other end of the wire through the grommet of the fireplace. This is the hole that the wire will go through.
- Run the wire through the drywall/wall until the ends of it reach the gang box on the wall. Sometimes, switches are installed directly instead of gang boxes as well.
- Connect the wire leads to the switch with the help of the flat screws.
- Check if the connection is right by turning on the fireplace once.
- Finally, close the switch up by screwing up the switch to the wall.
- Make the wire leads twisted in a way that doesn’t loosen up under pressure.
- If you’re using a mechanical timer, add that device to the wiring plan.
Problem 3 of 3: The Switch Isn’t getting Enough Voltage
This is one of the common issues, especially for fireplaces that have been used for a few years. And the reason for the problem is ‘millivolt loss’ across the system.
Thermopiles are supposed to produce 350 to 1000 millivolts and send them across the switch. If the voltage is significantly less than 350 mV, something is wrong.
Considering your switch and wiring are fine, a lack of voltage can happen for two reasons-
- A decayed or dirty wire.
- A dirty thermopile.
Below is the process to identify which of these two reasons you’re suffering. You’ll need a digital multimeter like Gardner Bender GDT-3190 for this troubleshooting.
How Would You Know?
Follow these steps to identify the reasons for millivolt loss across your gas fireplace thermopile or wire.
- Turn the pilot light on for 2 minutes.
- Unscrew the wall switch and locate the terminals.
- Unscrew the terminal screws and bring out the wire.
- Set the multimeter on DC Millivolt settings.
- Take the black and red leads from the multimeter and connect them to each switch terminal. Turn on the ignition switch to run electricity through the wiring.
- The multimeter will read and display the ‘millivolt’ it’s just got. Take note of it and call it ‘Switch Voltage’.
- Put the wire leads back to the terminals, and reset the switch.
- Put the multimeter leads on the control valve’s ‘TH’ and ‘TP/TH’ terminals.
- The multimeter will read a voltage. Note it down and call it ‘Thermopile Voltage’.
Now, cross-match the situations below and decide which part of the system is responsible for the low voltage situation.
Solution 1: Clean The Wires (If Switch Voltage < Thermopile Voltage)
This is the solution if you notice a significant millivolt loss across the wire. For example, if the switch voltage is 150 MV and the thermopile voltage should be 750 MV, you need to clean up the wire so it can conduct electricity properly.
Because a drop of about 120-100 MV is okay from the thermopile to the switch, but any more significant drop indicates mostly dirty or corroded wires.
Note that high voltage wires of 120V can keep that dirt/corrosion from building up. But a millivolt circuit is not like that. So, over regular use, it’s pretty usual to have a dirty wire blocking up the voltage required to open the gas valve. Also, oxidation and chemical reactions occur, reducing the capacity of copper wire to conduct electricity properly.
How to Clean A Corroded Wall Switch Wire
To clean up a corroded or dirty copper wire, follow the steps-
- Detach both ends of the wire. One from the switch terminals and another from the control valve.
- Trim down the old ends of the wires and bring out a couple of new ends. Do this on both the switch end and control valve ends.
- Take a steel wire brush and scrub the open ends of the wires.
- Once the contact points are restored, rejoining the wire leads to their places again.
- Make sure you’re not damaging any other parts of the connections such as switch terminals, screws, etc.
- If you want to go for chemical cleaning of wires instead of mechanical ones, follow this guide.
Solution 2: Clean The Thermopile(If Switch Voltage = Thermopile Voltage)
If both switch voltage and thermopile voltages are low(lower than 350 MV), then the problem is with the dirty thermopile. As it’s close to the fire area, there’s a good chance it will be clogged up by soot, dust, and dirt. And this will reduce its electric conductivity.
Cleaning it up will restore the voltage loss and let the wall switch function again.
Below are The Steps to Clean A Dirty Thermopile-
- Turn off the gas supply.
- Detach the wires around the thermopile, especially the TH, and TH/TP terminals.
- Use an air blower to gently blow out the loose dirt and dust from the terminals.
- Take a stainless steel brush and fine-grit sandpaper. Make sure the brush is small(about 150-200mm) in length. This one from Yaatao is our suggestion.
- Now, use the sandpaper and wire brush to clean up the soot and sticky dirt from the thermopile. You’ll know how much dirt is removed by just looking at it.
- To test if the problem is solved, re-read the multimeter reading. If it’s about 750-1000 MV, the job is done!
- Once the cleaning is done, reconnect the wires to the TH and TH/TP terminals.
Other Problems That Might Affect The Wall Switch
Sometimes, it’s not just the faulty switch; it’s a wire or the millivolt drop. A couple of other reasons might lead you to think your fireplace switch has gone bad.
Let’s talk about two such issues and how to deal with them-
The Ambient Temperature is Too Cold
As we know, the pilot light has to heat the thermopile for about 2 minutes to create the necessary electricity. But if it’s a frigid weather day, this might take way longer than 2 minutes.
If you are going through such a chilling temperature, keep the pilot light on for 4-6 minutes. If the switch doesn’t work, then try a few more minutes. At some point, the thermopile is supposed to be hot enough to generate 350-750 millivolts.
Alternatively, you can try adding a supercapacitor to the circuit. This will provide the necessary peak current for opening the valve.
The Pilot Flame isn’t Good Enough
Sometimes, the pilot flame might not be just good enough to heat up the thermopile. And if you don’t deal with fireplaces that often, you might not know how much flame is right either.
A short pilot light can happen for one of these reasons-
- Poor venting performance blocks sufficient oxygen flow.
- The gas regulator might be faulty.
- Gas might not be available enough or can have a weak flow.
- Insects like spiders can get into the gas pipe and block gas flow.
Try to review the list and find out which is causing a poor pilot flame. Maybe it’s time to replace the gas valve if you don’t find any.
Alternatives to Using A Fireplace Wall Switch
By now, you might think that wall switches are troublesome, although these problems are fixable. But it’s wiser and better to look for alternatives that will let you get rid of the wall switch whatsoever.
Therefore, we’ve picked up some wall switch alternatives for gas fireplaces that you can go with. Have a look-
Alternative 1: Use A Remote Control
This is a fundamental but practical replacement for an analog fireplace wall switch. This comes with a remote(with or without display), a signal receiver box, and wall mount accessories.
The receiver sits on the millivolt circuit from the thermopile to the gas valve. And once you turn on the pilot light, you can use the remote to turn the fireplace on.
It’s everything a wall switch would do but remote. Plus, it’s less troublesome than the issues we’ve discussed on wall switches.
Here are the best fireplace remote controllers we recommend-
- Best with ‘no’ display(on/off): Ambient On/Off Fireplace Remote Control
- Best with basic display: SkyTech SKY-3301
- Best for backlit display: Skytech SKY-3301P2
- The sleekest design: Skytech SKY-1001
Apart from our best picks, you’ll find dozens of other choices from Amazon.
Alternative 2: Use A Smart Remote Control
In 2021, everything had a ‘smart’ version, and so did your fireplace remote control.
A smart remote control lets you control the fireplace gas valve using WiFi, Bluetooth, and even your smartphone. It offers good control over the temperature and thermostat, has way more safety features, and sets a timer on the fireplace as instructed.
If you’re an intelligent home automation enthusiast, you’d love to have one of these and blend it up with the rest of your smart home ecosystem.
Here are our best choices of smart fireplace remote controllers-
- Best WiFi Smart Switch for Fireplace: Durablow SH3001
- Best for Controlling from Phone App: WiFire Millivolt Remote
Frequently Asked Questions
What does the wall switch do for a gas fireplace?
A gas fireplace wall switch protects the gas valve from accidentally turning on. It is a safety measure associated with a pilot flame and a thermopile.
What type of wall switch for a gas fireplace?
Gas fireplace wall switches are toggle switches that work at a ‘millivolt’ level. This means they operate within very low voltage(200-1000 millivolt) instead of a regular 120V switch.
What is the RS switch on the gas fireplace?
RS or Room Switch is a wall switch that helps you to both remote-control and manually turns on/off the gas fireplace. It has three modes- On, Off, RS. HHT SRV41D0048 is an example.
Does a gas fireplace switch work without electricity?
Yes, gas fireplace wall switches don’t need any electricity to run. It runs in a millivolt circuit where the thermopile thermocouple provides the electricity on the gas valve.
How to turn on the gas fireplace with the wall switch when power is out?
The gas fireplace switch doesn’t have anything to do with your house’s power. You can use it as usual even when the power is out.
Why does my gas fireplace have 2 switches?
Gas fireplaces can sometimes have two switches to let the user remotely and physically control the fireplace. The smart switch can be remote-controlled and the other one is manually operated.
What to do if I can’t find a switch for the gas fireplace?
Open the switches and look at the wires that they’re connected to. The fireplace switch will have 18 gauge, thin wire, and thicker 12 or 10 gauge.
Can you add a wall switch to a gas fireplace?
Yes, you can. Most fireplace control valves have a thermopile with TH and TH/TP terminals. These are the places where you can connect a switch and install it on your wall switchboard.
HVAC tech with over 30 years of experience. Retired and doing repair work on the side around Madison County, AL.