Informational Guide

How To Bypass A Thermal Switch On Water Heater

Does your water heater thermal switch keep tripping? Learn how to bypass a thermal switch in our comprehensive guide.

by Holly Curell

Thermal switches are added to gas heaters as a precaution; they self-activate when things seem to deviate from the set standard.  

Typically the switch trips – stopping electric supply to the burner – when the heater's vents are jammed, leading to excess buildup. Also, the thermal switch might trip when it detects flammable vapors near the heater, like paint fumes or gasoline.

However, if your water heater thermal switch keeps tripping now and then, it would be best to get in touch with a specialist, or you can bypass the thermal switch entirely. 

Your water heater's thermal fuse looks like a thin white plastic strip with wires coming out of each end. To bypass, use an electrical tape or a wire nut to hold both ends in place.   

However, if the two wires going through your thermal safety are connected with a wire nut, that is obviously not a very safe thing to do.  

Therefore, only use a wire nut when inspecting and running diagnostics; in short, only consider this option as a temporary means of bypassing. 

Bypass Thermal Switch On Water Heater

How To Reset The Thermal Switch On A Water Heater 

Thermal switches cut off critical machinery current when temperature limits exceed to prevent any potential failure or burnout.  

To know how to reset the thermal switch on a gas water heater or how to reset the Whirlpool water heater go through the following steps: 

  1. 1
    Find the reset button on the thermal switch's center, and press it 
  2. 2
    When it trips, you will hear a clicking sound. 
  3. 3
    If no clicks are heard, try lighting the pilot using the given instructions attached to the unit. 
  4. 4
    If your water heater's Status Light starts flashing, the thermal switch has probably tripped. 

However, how to resolve the issue if the water heater's thermal switch does not reset because of a faulty thermostat? 

Also, if tripping is no longer an odd occurrence, it might be due to a high-limit switch. This happens because your thermostat is not efficiently managing the heat.  

The high limit switch trips typically when the temperature reaches dangerous levels. Obviously, you do not want to wash hands with boiling water; therefore, this feature is essential. The switch will continue tripping until you have a newer thermostat.  

Also, inspect the breaker, and please ensure that the right sized breaker is installed, one meant to support water heaters.  

Related Article: How To Reset Water Heater (Guide For Electric & Gas)

Reset The Thermal Switch On A Water Heater

Why Does My Water Heater Thermal Switch Keep Tripping? 

There can be multiple reasons why your water heater thermal switch keeps tripping. Let's delve in: 

Bad Thermostat 

If you have an electric water heater, it typically has two heating elements and two thermostats. The thermostat keeps track of the heater tank's water temperature and shuts off the heat source when it reaches the desired level.  

However, when a thermostat turns bad, it may fail to turn off the heating element. Consequently, the water continues to heat, leading to the reset button tripping. If this is the case with your heater, the thermostat needs to be replaced. 

Learn More - How To Test Water Heater Thermostat (Guide Using Multimeter)

Loose Connection  

High resistance due to loose wires can lead to a fire hazard. Therefore, if loose electrical connections inside your water heater, your thermal switch may eventually trip irrespective of the water temperature.  

Related Article - Should I Replace My Water Heater Before It Fails? (When To Replace)

Faulty Heating Element

If the heating element is acting up, the power may continue to flow despite the thermostat signaling to halt. 

Unfortunately, this means that it continues to work, raising the heat beyond acceptable levels, which eventually leads to the thermal switch tripping.  

Learn More: Signs Water Heater Is Going Bad: Most Common Causes

Bad Thermal Switch 

The installed thermal switch may suffer from wear and tear, leading to hindered performance. If such is the case, it may constantly trip irrespective of the water temperature.  

Remember, the thermal switch is the part of the upper thermostat; therefore, if this problem arises, you will have to replace the entire thermostat.  

To test a water heater's thermal switch, perform the following steps:  

  1. 1
    Check via a multimeter at a lower resistance. 
  2. 2
    Attach the multimeter to the terminals to rule out if there are any connection issues between the two probes. 
  3. 3
    In case there is no reading, the thermal switch has failed, hence replacing it cannot be avoided. 

What Is a Thermal Switch & How Does It Work?

A thermal switch, aka thermal cut-off switch, is an electromechanical device that activates and deactivates electrical flow based on temperature changes.  

Basically, the switch trips to prevent potential failure or burnout when the temperature exceeds a pre-defined range.  

These handy devices are used in homes as well as industrial settings. Thermal switches are usually found in home appliances like tankless water heaters and dryers in the most basic form. 

Whereas their commercial and industrial application includes use in sophisticated equipment like commercial jetliners.  

In a standard residential hot water heater, the thermal cut-off switch is resettable manually and is located at the front of your heater's combustion chamber door.  

Thermal Switch Water Heater

Is It Safe To Bypass A Thermal Switch? 

You might be wondering whether it is a bad idea not to use a thermal switch. Well, it's designed to ensure safety; therefore, you cannot disregard its need and importance.  

In a nutshell, it safeguards you from water heater-related dangers; for example, the thermal switch will activate when gas valves get stuck with the burner on, protecting you from a potential explosion.[1 

Basically, it comes into play if your water heater valve gets stuck and the temperature and pressure relief valve fail to open to disperse overheated water and excess water pressure.  

On the other hand, if the thermal safety switch has been disconnected or bypassed, heated water and pressure will go way above the required level. 

With that said, if you are thinking, "can I bypass a thermal switch on a water heater," the answer is you can, but there are many risks involved.  


How do I know if my thermal switch is working? 

You can test it out using a multimeter. Connect the switch to your digital multimeter and watch the display to know whether it needs replacement.[2] A functioning thermal switch will make the needle move to '0', whereas the needle won't move if the unit is faulty.   

How long do thermal switches normally last? 

You can expect a good thermal switch to last around ten years.  

Can I replace the thermal switch on my water heater? 

Yes, you can replace a thermal switch on your water heater, but you would have to replace the upper thermostat entirely as the switch is a part of it.  

How much is a water heater thermal switch? 

Since a water heater thermal switch does not come separately, the cost of repairs or replacement of a thermostat is around 150 to 200 USD.  


Bypassing a thermal switch on a water heater can be considered quite unsafe for several reasons. 

That is why you mustn't do it without proper safety gear. For best results, please call in a professional! 




Holly Curell is the editor extraordinaire for Plumbing Lab. Having grown up in Michigan, Holly has spent time living in New York, Virginia, & currently North Carolina, where she lives with her husband & family. Holly loves DIY & has years of experience with at-home plumbing problems that arise from having 3 kids & living in colder climates. When she's not writing about her plumbing knowledge, Holly enjoys reading, hiking & relaxing with family.