Honeywell Water Heater Pilot Light Won't Light? (We Have A Fix)

Upgraded Home Team
by Upgraded Home Team
Honeywell water heaters are great until the pilot light won’t light. The pilot light on a Honeywell water heater won’t light when there is a problem with the thermopile unit controller. Whether it be identifying the problem or replacing the thermopile unit controller, let’s take a look at what you can do to fix a Honeywell heater when the pilot light won’t light.

Nothing jolts you awake in the morning like jumping into a cold shower. Along with the frustration of being doused with cold water, you realize that your water heater isn’t working. You may go to troubleshoot and find that the pilot light isn’t on. Then, no matter how hard you try, you just can’t get it to stay lit. What does t his mean? Why won’t the pilot light to your Honeywell water heater light?

Many Honeywell water heaters may have an issue with the thermopile unit controller. This issue causes the controller to display a “Low Voltage Error” code. The controller can be replaced by your plumber while the water heater is under warranty.

We’ll help you understand how to troubleshoot your own Honeywell water heater pilot light issues, as well as similar issues with other types of water heaters. We’ll also explain what a pilot light is so that you can understand more about the inner workings of what you’re dealing with.

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What Is A Pilot Light?

What if you don’t have a thermopile unit controller? To diagnose, you need to understand how the pilot light works. A pilot light is a small flame that continually runs in your gas appliance. When you turn on your shower or hot water tap, the hot water flows out to the fixture. When you need hot water, the gas valve will open up and the pilot light will ignite the fuel.

In a tank-type water heater, the burning gas heats up the water inside the tank. In a tankless water heater, the burner heats up water as it passes through a coil.

Whether the pilot light is lit or not, a small amount of gas continues to flow from the gas line. The pilot light would combust the gas, turning it into heat and flue gases. Without the pilot light, gas could continue to fill up your water heater closet or garage.

How To Fix A Honeywell Thermopile Unit Controller Error

Most Honeywell pilot light issues stem from the pilot light unit controller. Specifically, this is the thermopile unit controller. The error message will say “Thermopile Low Voltage.” When you get this error, the only fix is to replace the whole thermopile unit.

Many unit controller issues should be apparent while the appliance is still under warranty. If you find the error within that warranty period, the manufacturer should work with you to get it replaced at no or low cost.

If your unit is out of warranty, you can try to replace it yourself. These replacements can be purchased online for around $50. Do not try to fix it yourself while your water heater is under warranty, as you could void the warranty.

What Is A Honeywell Voltage Low Error?

Honeywell water heaters with electric controls have a common error reading that says “thermo-pile voltage low.” Some statistics say that almost 1% of all Honeywell water heaters will have this error. In manufacturing, that’s quite high! If the voltage is low, the thermo-pile won’t be able to operate correctly.

Unfortunately, this error isn’t exclusive to Honeywell water heaters. Many other types of water heaters use the same Honeywell thermo-pile controller.

How To Reset Your Honeywell Water Heater

How Do You Light A Pilot Light?

Occasionally a pilot light may go out on its own accidentally. This could be because of a strong draft or a power failure. Most new water heaters should be able to reignite the pilot light on their own.

  • Light your pilot light with a barbeque style lighter. If your water heater can’t relight the pilot light, you may need to use a lighter to relight it. Your water heater should have a button to use when relighting.
  • Push the button while lighting. You will need to push it down as you hold the flame of your lighter up to the pilot light tube. Think of it like lighting a gas grill.  If you’re successful, you will see a small flame coming from your pilot tube.
  • Hold the button down for a few seconds longer. If it’s not lighting, hold the button down for 3 seconds before attempting to light. Then, make sure the flame is not too big or too small before closing the door.

Manual vs. Electric Valve Controls

The thermocouple in manual units, and thermo-pile in electric units, measure the temperature at the pilot light to ensure that the flame is working. To switch between the pilot light and full heating mode, the gas valve needs to open and shut. Older or low-end appliances, the gas valve might be manual.

Difference Between Thermopiles And Thermocouples

Manual valves use what’s called a thermocouple. The thermocouple senses heat from the pilot light. If the pilot light burns out, the thermocouple senses a lack of heat and sparks the pilot light. Newer or higher-end appliances may use an electric gas valve controller. These controllers use what’s called a thermo-pile.

Thermopile Power Issues

Since the gas valve requires an electrical connection, it may be possible that a power failure or a worn-out wire may have prevented the valve from opening. When troubleshooting your hot water heater, check to ensure that the correct voltage is reaching your gas valve.

Most Honeywell water heaters with electric gas valves need just 12 volts for the valve to work. Use a Multimeter to check the voltage drop across the valve. If it reads less than 12 volts, you may need to replace your gas valve or controller.

Other Issues That Cause Pilot Light Outages

If you don’t have any error codes on your Honeywell thermocouple unit, there could be other causes of pilot light errors. Some other issues that cause issues lighting the pilot light may include fouled pilot tubes or power failures.

Dirty Pilot Tubes

If you see dark stains around the pipes, there could be deposits in the tube that prevent gas from coming out properly. Try having the pipes properly cleaned. Since this may require disassembling the gas piping, make sure the gas lines are shut off before proceeding with any work.

Faulty Wiring

Damaged wiring could also cause issues keeping the pilot light lit. Check all the wiring to and from the controls and valves. If you suspect any of the wiring has been damaged, pinched, or disconnected, call an electrician to repair the damage. If the damaged wiring is on the appliance, you may need to replace the unit.

Backdraft Causing Pilot Light Issues

If you don’t have an error on your Honeywell thermo-pile unit, your pilot light issues may be due to the environment. Your water heater should be installed in a neutral environment. This means that you don’t want excessive drafts in and out of your space.

Every gas water heater needs combustion air. Combustion air is fresh outside air that is used for the process of combustion. Gas is a fuel that needs to be ignited, a chemical process that needs oxygen.

Troubleshooting Backdraft Issues

If you can feel a breeze or draft in the location where your water heater is stored, this draft could cause your pilot light to be blown out frequently. If your unit controller doesn’t have any error codes, this backdraft could be the issue.

Try testing the pilot light, timing how long it stays lit. With backdraft issues, the pilot light may stay light for random amounts of time.

Make sure that the flue vent on the top of your water heater has been installed correctly. There should be a small gap between the duct at the top of the water heater. This helps make sure that the flue gases rise up through the duct and out of your home rather than recirculating back into space.

Be Careful Around Faulty Gas Appliances

If you’re in doubt with what could be wrong with your pilot light, call an expert. Gas can be very dangerous. Small leaks can fill the space you’re working in, small sparks can ignite the odorless gas. Even if you don’t start a fire, gas can be poisonous.

Be sure to check out some of our other articles about water heater issues, such as when the water heater only gets lukewarm or why water might leak from the bottom.

Are You Worried About A Gas Leak?

If you suspect any type of gas leak, it is wise to call a professional. Since the gas is extremely dangerous, this is not something you want to try to fix for yourself. If you smell gas in your home, you’ll want to remove your family, as well as any pets or live creatures, and then go to a neighbors and call for help.

Do You Need Water Heater Repair Services?

Get free, zero-commitment quotes from pro contractors near you.

Wrapping It Up

If your pilot light is not lighting, you may have an issue with the thermopile unit controller. More often than not, with this type of problem, the controller will need to be replaced. This should not be attempted as a DIY project. Therefore, you will need to call a professional to come to install a new thermopile unit controller onto your Honeywell water heater. Then, your unit will work like it’s brand new!

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Upgraded Home Team
Upgraded Home Team

We are a team of passionate homeowners, home improvement pros, and DIY enthusiasts who enjoy sharing home improvement, housekeeping, decorating, and more with other homeowners! Whether you're looking for a step-by-step guide on fixing an appliance or the cost of installing a fence, we've here to help.

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