How to Troubleshoot and Fix a Water Heater That Won’t Heat

A sudden lack of hot water can be frustrating, especially when your water heater stopped heating at the most inconvenient time. Whether you’re dealing with an electric or gas unit, this guide will help you understand common reasons why a water heater stopped heating and how you can troubleshoot and fix the problem yourself.

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 troubleshooting information provided in this article is based on general service manuals and 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.

Common causes for a water heater that won’t heat

There are several common issues that can cause a water heater to stop heating water. Let’s dive into the most frequent culprits for both gas and electric water heaters.

Electric water heater 

If your electric water heater won’t heat, here are some possible reasons for the malfunction:

• Blown fuse or tripped breaker: One of the most common reasons your electric water heater will not heat is due to a blown water heater fuse or a tripped breaker. Start by checking your circuit breaker panel for a tripped breaker or a blown hot water heater fuse. If your unit is running on a 240v power supply, it requires two breakers. Make sure both are fully switched on.
• Faulty heating elements: Electric water heaters rely on heating elements to warm the water. If one or both of these elements fail, you’ll quickly notice that your 240v water heater stopped working. Testing and replacing the heating element could fix the issue.
• Thermostat failure: Another common reason your water heater stopped heating could be a malfunctioning thermostat. The thermostat regulates the water temperature inside the tank. If it’s not working, the water heater won’t turn on to heat the water.

Read more: Why your water heater smells like rotten eggs and how to fix it

Gas water heater

Gas water heaters face different challenges than electric units. Here’s what could be wrong if your gas hot water heater stopped working:

• Pilot light issues: One of the first things to check when your gas water heater stopped heating water is whether the pilot light is on. A draft, faulty thermocouple, or gas supply issue could extinguish the pilot light, stopping your heater from working. If the water heater igniter won’t spark, the issue could be with the ignition system.
• Faulty thermocouple: If your water heater keeps shutting off, it could be due to a bad thermocouple. This safety device turns off the gas supply if the pilot light goes out, but if it’s malfunctioning, it might mistakenly shut off the gas even when the light is still on.
• Blocked or dirty burner: If the burner is dirty or clogged, your gas hot water heater stopped working because it’s not able to generate enough heat. Cleaning or replacing the burner could solve this issue.

Read more: Common gas water heater problems & how to fix them

Safety precautions

When working on any appliance, remember to keep safety first. Here are some tips to keep in mind: 

• Always power off and unplug your appliance or switch off the circuit breaker before attempting any maintenance or replacement work. This keeps you safe by preventing any risk of injury from electric shock.
• Wear insulated work gloves to protect your hands from sharp metal parts, pinching hazards and debris.
• Take your time and don’t rush while working to prevent accidents and personal injuries.
• Work in a well-lit area so you can clearly see and access the interior parts.
• Clear your workspace of clutter and other obstacles. Keep children and pets away from the work area.
• Never work on internal parts with bare wet hands. Make sure the work area is completely dry.
• Check your user manual to see if there are specific installation or safety instructions for your part or appliance. 
• Be gentle when handling or removing parts. Excessive force might damage the appliance or cause injury.
• Wear safety glasses when working with chemicals, dust or cleaning large debris to prevent injury. 
• If the appliance has recently been used, give it plenty of time for any heating parts to cool down before working on it. 
• Take pictures or make a note of wiring terminals or other connections before disconnecting to prevent any problems with reassembly.
• 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.

General Troubleshooting Steps (For Both Gas and Electric Models)

Check the thermostat settings:

1. Make sure the thermostat is set to a temperature high enough for heating (around 120°F is ideal).
2. If it’s set too low, simply adjust it to a higher temperature.

Inspect the circuit breaker (Electric Water Heaters):

1. If you have an electric water heater, check the circuit breaker to ensure it’s not tripped.
2. If the breaker is tripped, reset it by switching it off and on again. If it continues to trip, it may indicate a problem with the heating elements or electrical wiring.

Check the gas supply (Gas Water Heaters):

1. If you have a gas water heater, make sure the gas supply valve is turned on.
2. Check if other gas appliances in your home are working properly. If they aren’t, there may be a problem with the gas supply.

For Gas Water Heaters

Check the pilot light

1. Turn off the gas supply and wait 5 minutes to clear any gas fumes.
2. Locate the pilot light assembly (usually near the bottom of the water heater).
3. Follow the manufacturer’s instructions to relight the pilot light. Generally, this involves pressing and holding the pilot button while using a match or lighter to ignite the flame.
4. Once the pilot is lit, release the button and ensure the flame stays on.
5. If the pilot light doesn’t stay lit, the thermocouple may be faulty.

Check the thermocouple

1. The thermocouple is responsible for detecting the pilot light. If it’s malfunctioning, the heater won’t stay lit.
2. Use a multimeter to check the thermocouple for continuity.
3. If the reading is negative or the thermocouple is visibly damaged, it will need to be replaced.
4. To replace the thermocouple, turn off the gas, unscrew the old thermocouple, and screw in the new one, ensuring it’s positioned correctly in the pilot assembly.

Check the gas control valve

1. If the gas control valve isn’t sending gas to the burner, the heater won’t function.
2. Use a multimeter to check the continuity of the gas control valve.
3. If it’s faulty, the valve will need to be replaced. Make sure to replace it with a model compatible with your water heater.

Inspect the burner

1. Check if the burner is dirty or clogged with debris.
2. Turn off the gas and remove the burner.
3. Clean it with a brush or compressed air to remove dirt and debris.
4. Reinstall the burner and check for proper ignition.

For Electric Water Heaters

Check the heating elements

1. A common cause of an electric water heater not heating is a faulty heating element.
2. Turn off the power to the water heater at the circuit breaker.
3. Remove the access panels to expose the heating elements.
4. Use a multimeter to check the heating elements for continuity.
5. If the element does not show continuity, it needs to be replaced. To replace it, use a wrench to unscrew the faulty element, remove it, and screw in the new one.

Check the high-limit thermostat

1. The high-limit thermostat prevents the water heater from overheating. If it’s malfunctioning, it could prevent the heating elements from working.
2. Use a multimeter to check for continuity on the thermostat.
3. If the thermostat does not show continuity or is visibly damaged, it will need to be replaced.

Check the temperature and pressure relief valve

1. The T&P valve releases excess pressure, but if it’s faulty, it can prevent the water heater from functioning properly.
2. Turn off the power and water supply to the heater.
3. Inspect the T&P valve for leaks or signs of malfunction.
4. If it’s faulty, replace it with a compatible valve.

Check for sediment buildup

1. Over time, mineral deposits can build up inside the tank and around the heating elements, reducing heating efficiency.
2. Turn off the power and water supply.
3. Drain the tank and flush it out to remove sediment.
4. If needed, clean the heating elements or replace them.

If you’ve gone through all these steps and the heater is still not working, or if you need help finding replacement parts, visit our repair help section for more information and troubleshooting support.

Wrapping up

Thanks for reading! If you have any other appliance repair needs or projects, you can find more resources including our DIY blog at AppliancePartsPros.com. There, you can enter your model number to order the exact parts you need. Most orders arrive in two business days.

You can also reach our award-winning customer service team at 1-877-477-7278, chat with a pro on our website, and watch thousands of free video tutorials on our YouTube channel.

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