Guide To Troubleshooting A Hot Tub High Limit Switch


Imagine this – lifting the cover of your hot tub ready to jump in only to realize the water is cold! Frustrating, isn’t it? But there is no need to worry. There is a possibility that your high limit switch has tripped to prevent your spa from overheating.

Okay, for the sake of hot tub owners who are not well acquainted with their equipment, a high limit switch is simply a feature that is built into spas for safety purposes. How it works is that it deactivates the heater when the hot tub temperature hits extreme numbers.

Several reasons could make this temperature sensor to switch to a flip. Finding these out will help you perform an effective hot tub temperature sensor troubleshooting and get your spa up and running.

Where Do You Find The High Limit Switch In Your Hot Tub?

As long as our spas are working fine and giving us the relaxation we seek, most of us will never know things like a high limit switch exist in our hot tubs. It’s until something happens to the switch and the water gets cold that we begin to wonder what is going on. So let’s make things a little easier for you and tell you where you can find your temperature if things ever go wrong and it trips.

A limit switch will be located in your heater enclosure, mostly in its lower-left corner. It is usually white in color with a red button at the center. If your water is not heating up and you think the heater is the problem, one heater element that you need to check out will be the limit switch.

Common Hot Tub High Limit Switch Issues


When the temperature of your water gets unsafe, the high limit switch breaks the circuit such that electricity doesn’t reach your hot tub heater. Here are some of the things that will cause this device to trip.

1. Air Is Trapped In Your Equipment

If you just drained and refilled your hot tub and suddenly your limit switch started tripping, then there could be airlocks in your system. When the air gets trapped in your equipment pipes, it interferes with the flow of water through the heater. This means that it receives less water than required or none at all.

When your limit switch senses this problem, it flips to prevent the dry fire that could damage the heating element.  To fix this problem, get rid of the trapped air. Reset the switch and see if it still flips. If it doesn’t chances are good that it was just air and you can go ahead with your soak without worrying much about your spa.

2. Your Filter Is Dirty

The filter is responsible for keeping dirt particles and elements away from your spa. If you have not cleaned it for a while, it could make your temperature sensor switch to a flip.

When the filters are clogged with debris, they reduce the circulation such that the heater is starved of water. If the rate at which the water flows into the jets is reduced, it means that your spa skimmer too will not be receiving enough water. As such, it will start sucking in the air instead, which could damage the heater. Your high limit switch will flip to prevent this from happening.

For fruitful hot tub temperature sensor troubleshooting, remove your filter and give it a thorough cleaning. If you have two of them, the better, as you can swap these when you do the cleaning. Once you have put the filter back, try flipping the switch on and see if it trips.

3. Your Heater Is Corroded

When corrosion attacks your equipment, you can experience an ocean of problems with it from limit switch issues to a hot tub tripping breaker. All these will affect how your spa heats.

To find out if the problem with your high limit switch is caused by rust, inspect your wiring, the heater, and any other component that is prone to corrosion. Find out especially how much the heater has been affected by it. If it has completely been eaten away, you will need to get a new one. Doing a replacement could be all you need to stop the misbehaving switch.

4. There Is A Problem With The Thermostat

Check your thermostat. It could be that it is marked wrongly. If it is calibrated too high, it may not be able to give the right temperature reading and this will automatically cause your limit switch to flip.

Your high limit switch troubleshooting will involve recalibrating the thermostat. Turn the high limit switch back on to see if the problem has been fixed. If not, check the contactor to see if it is working properly. It needs to open when the thermostat turns on and close when it turns off. If this is not the case, get a new contactor, and test your spa to see if the switch is still tripping.

Remember This!

Hot tub temperature sensor troubleshooting can be pretty easy when you have experience in electrical systems. However, things can get really ugly if you are not quite familiar with the repair you are about to do.

Your safety comes first and if you are not comfortable working with electric gadgets, just get a professional involved. Of course, it will cost you a few bucks but you will have saved yourself a lot of time and trouble.

Globo Surf Overview

A high limit switch is an important hot tub component and you should never ignore a problem with it, however small it might seem. If you don’t want to damage your heater or spend more money than necessary in repairing your equipment, it would be wise to perform a hot tub temperature sensor troubleshooting as soon as you notice something unusual.

Your best bet would be to find out what is causing the problem and work it out from there. Also doing regular hot tub maintenance will help you identify potential issues with your limit switch and solve them before they happen.

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My name is David Hamburg. I am an avid water sports fan who enjoys paddle boarding, surfing, scuba diving, and kite surfing. Anything with a board or chance I can get in the water I love! I am such a big fan I decided to start this website to review all my favorite products and some others. Hope you enjoy!