How to change a thermocouple on a gas water heater: A step-by-step guide

If you had to take an ice-cold shower because your water heater refuses to heat up, don’t worry — it could just be a thermocouple problem. The good news is that changing a thermocouple isn’t as scary as it sounds, and you can do it yourself with a few tools and a little patience. We’ll show you how to swap out that faulty thermocouple and restore your water heater.  

If you need any replacement parts for your appliances, you can enter your model number at AppliancePartsPros.com to order them. Most orders arrive in just two business days, and we have thousands of free guides to show you how to install your new parts.

Important: The information provided in this article may not apply to your specific appliance model. While we strive to offer helpful advice for DIY appliance repairs, variations in models and configurations can lead to differences in troubleshooting steps, error codes and part replacements. For the most accurate guidance, we strongly recommend consulting the technical sheet for your specific appliance model.

Why would a water heater thermocouple fail?

A water heater thermocouple can wear out over time due to several factors, including:

• Normal wear and tear
• Dust and debris buildup, which can interfere with the thermocouple’s ability to detect the pilot light
• Bending or damage

Symptoms of a faulty thermocouple

Here are some signs your thermocouple may be faulty.

• Pilot light won’t stay lit: If the pilot light ignites but goes out after releasing the gas control knob, the thermocouple might not be sensing the flame.
• No hot water: If the burner never ignites, even with a lit pilot light, the thermocouple could be to blame, which may prevent you from getting hot water. 

How to change out the thermocouple

Follow these steps to replace the thermocouple in your water heater.

What you need

• Adjustable wrench
• Screwdriver
• New thermocouple (make sure it’s compatible with your specific water heater model BEFORE ordering one)

Safety precautions

When working on any appliance, always keep safety first to avoid personal injury or damage to the appliance or its parts. Here are some tips to keep in mind:

• Always power off and unplug your appliance or switch off the circuit breaker before you attempt any maintenance or replacement work. This keeps you safe by eliminating any risk of electric shock. 
• If the appliance has recently been used, give it plenty of time to cool down before working on it. 
• Shut off the gas supply to prevent any gas leaks while you work. 
• Take your time while working to prevent accidents and personal injuries. Rushing is the enemy of precision.
• Work in a well-lit area so you can see and access appliance parts.
• Keep your workspace free of clutter and other obstacles. Keep children and pets away from the work area.
• Never work on internal parts with wet hands. Make sure the work area is completely dry.
• Check the user manual to see if there are specific installation or safety instructions related to your appliance or replacement part. 
• Be gentle when handling or removing parts. Excessive force might damage the appliance or cause personal injury.
• Wear insulated work gloves to protect your hands from sharp metal parts and debris.
• When working with wires, avoid touching any exposed wires or terminals. If you need to touch a wire, use a non-conductive tool or wear insulating gloves to prevent electrical shock.
• Always take photos or make a note of wiring terminals or other connections before disconnecting them to make reassembly easier.
• Consider wearing safety glasses and/or a dust mask when working with chemicals, dust or a large amount of debris to prevent irritation or injury.
• Turn off the water supply at the outlet before beginning repairs. Keep towels ready to catch any residual water in the system when removing parts.

Replacement process

Follow these steps to change out the thermocouple on your water heater.

1. Find the gas supply valve and turn the gas supply to the “OFF” position so no gas flows while you’re working on the unit.
2. Use a screwdriver to remove the screws that hold the access panel in place.
3. Use an adjustable wrench to carefully disconnect the gas line, pilot tube, and thermocouple from the gas control valve.
4. Find the thermocouple next to the pilot light. Carefully pull it out of the burner assembly.
5. Inspect the thermocouple for any visible signs of damage, such as bends or soot buildup.
6. Slide the new thermocouple into place next to the pilot light.
7. Secure the thermocouple, gas line, and pilot tube back into the gas control valve. Make sure all connections are tight (but not overtightened) to prevent gas leaks.
8. Turn the gas supply back on.
9. Relight the pilot light by following the manufacturer’s instructions. The pilot light should stay lit and the burner should ignite.
10. Reattach the access panel to the water heater.

Troubleshooting tips

If the pilot light still won’t stay lit after replacing the thermocouple:

• Make sure all connections are secure and that there aren’t any gas leaks.
• Inspect the pilot light. A weak or flickering pilot light could indicate issues with the gas supply or pilot tube. Cleaning the pilot tube may resolve this.
• Check that the thermocouple is aligned with the pilot flame. It should be close enough to detect the flame, but not touching the flame directly.

Frequently asked questions

Find answers to some of the most common questions about water heaters.

How much does it cost to replace a thermocouple on a water heater? 

A new thermocouple can cost about $10 to $20 for the part itself. If you hire a professional to replace it, the labor cost can bring the total to around $100 or more.

How long does a water heater thermocouple last? 

A thermocouple typically lasts around 10 years, but it may wear out sooner due to dirt buildup or more frequent use.

Can I replace a thermocouple on a water heater myself?

Yes! If you’re comfortable with using tools and have general knowledge about water heaters, replacing the thermocouple should be a relatively simple task.

Is a thermocouple the same for all water heaters? 

Thermocouples come in different sizes and configurations, so it’s important to get a replacement part that’s compatible with your specific water heater model.

Additional information

Thanks for reading! If you need any replacement parts, grab your model number and head over to AppliancePartsPros.com. We have over two million parts in stock and most orders arrive in just two business days. If you need some help with finding the right part or placing an order, you can contact our team at 1 (877) 477-7278.

While you’re waiting for your new part to arrive, you can explore our DIY blog and watch thousands of video tutorials on our YouTube channel.

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