Why is My Lay-Z-Spa Not Heating Up? (Causes & Solutions)


Your Lay-Z-Spa may not be heating up properly. If this happens to you, there are a few possible reasons to consider.

You may be experiencing a malfunctioning limit switch or it could simply be that the filter is dirty.

If the spa was purchased several years ago, you may have a solid state probe or capillary bulb. If you think your spa is old and you don’t remember changing the filter, contact the spa manufacturer for more information.

High limit switch malfunctions

When the high limit switch in your Lay-Z-Spa starts to trip, it may be the fault of your hot tub’s thermostat.

A high limit switch is a mechanical device that senses the temperature of water using a bulb and capillary tube.

These parts are located in the THERMOWELL, where you can also find the thermodisc.

When you refill the spa, this sensor will be triggered, causing it to trip the high limit switch.

To reset the high limit switch, you should press the large red button on the spa pack. If you cannot fix the high limit switch yourself, it is important to call a professional.

You can damage other parts of the equipment in the spa if you try to repair the high limit switch by yourself.

The first thing to do if you suspect your spa’s high limit switch is to check the thermostat.

A broken or misplaced thermostat could cause the hot water to reach a temperature more than 20 degrees below the set temperature. Another possibility is that your pressure/flow switch is malfunctioning or stuck closed.

This will stop your heater and likely your jets. Another possible cause is a buildup of calcium in the system.

The high limit switch in your Lay-Z-Spa works to prevent your hot tub from becoming too hot. If the temperature in the thermowell rises to over 120 degrees, the high limit switch will break the circuit, and turn off the heater and pump.

It will also shut down your hot tub completely. If you want to be able to use the hot tub, make sure your high limit switch is functioning properly.

This device prevents a hot tub from getting too hot, which can be dangerous to bathers.

Dirty spa filter

If you’ve noticed your hot tub has been acting strange lately, chances are it’s because of a dirty spa filter. It could also be due to pump air lock or closed slice valves.

Other causes of overheating include improper water levels, low water pressure, and continuous filtration. Ideally, you should filter your spa once every 12 hours.

However, if you’re not able to keep up with that, there are other things you can do to increase its flow rate.

A dirty filter is one of the first things to check when you notice a slow water flow. Other causes include a blocked or closed valve, a clogged jet, or a broken pump impeller.

Clogged spa drain cover

Another possible cause of low water flow is a clogged spa drain cover, low water level, or other obstructions. In addition, your hot tub’s heater may have a screen on the inlet side, which can be clogged. If this is the case, cleaning or replacing the inlet screen should fix the problem.

If you’re able to fix the problem yourself, you can save yourself a lot of troubleshooting time by doing routine maintenance.

A dirty spa filter is likely to shut down the hot tub and display error codes. If you don’t do it soon, you’ll risk damaging the pump or hot tub cover.

But if you’re determined to restore your hot tub to working condition, it’s worth the effort.

And don’t forget to take advantage of the many benefits of proactive maintenance: clean water circulation and a healthy PH balance.

If your hot tub has a heater, check your temperature sensor. This isn’t the same as a thermostat, but it plugs into the main circuit board. It has a probe that fits into the thermowell and should be checked for damage.

If your hot tub displays an incorrect temperature, the temperature sensor may be faulty. It may be a matter of a loose connection near the pump or heater.

Older spas have capillary bulbs

Unless your hot tub is equipped with a thermometer, the temperature control can be an issue. There are two types of thermostats: mechanical and solid state.

Older spas have mechanical thermostats that lack a digital panel display, while newer models have a temperature sensor built into the circuit board.

Test your spa’s thermostat with an ohm meter to make sure it is engaged. If it does not respond to your input, you may have a faulty sensor.

Mechanical thermostats have been used on spas for years, but they are less common than electronic thermostats.

Electronic thermostats employ thermistors in bulb-like sensing units. The disadvantage of mechanical thermostats is that they can be unpredictable and are susceptible to the same problems as equipment packs.

Thermostats also work better in dry-wells. Nevertheless, you must make sure to check your spa’s manual to make sure it’s properly calibrated.

If your hot tub has a high limit switch, you must follow the manufacturer’s instructions for adding water.

Adding water to a spa differently from the instructions will likely cause the high limit switch to trip.

If you’re unsure whether the switch is malfunctioning, try pressing the big red button on the spa pack to reset it. If you’re still experiencing the same problem, you may need to replace the entire switch.

Ensure that the water flow through the heater chamber is adequate for proper heating.

Older spas often contain a pressure switch in the heater chamber, which is intended to protect the heating unit from overheating the spa.

If the water flow is too low, the pressure switch may shut down the spa’s electrical circuit and prevent it from heating up. If you’re able to fix this issue, your spa should start getting heat again.

Older spas have solid state probes

Modern hot tubs have two high limits – one for the inside heater and one for the outside. If you notice an error code indicating that a high limit has been exceeded, it will be displayed on the spa’s control panel.

Those older than 20 years commonly use a mechanical thermostat with a capillary bulb. A simple test to see if the thermostat is functioning properly can help you diagnose the problem.

If your hot tub is not producing heat, it’s probably the thermostat. Most older models use a mechanical thermostat, while newer spas have solid state probes.

Check the thermostat and look for corrosion. If it’s corroded, you may need to replace the entire thermostat. If the switch is engaged, test it with an ohm meter to make sure it’s functioning properly.

You’ll know if it’s engaged if it makes a low clicking noise.

Checking for voltage at the heater terminals

If your hot tub is not reaching the correct temperature, it might be the heater or the control board. If you have the opportunity to test it yourself, you can check the voltage at the heater terminals using a multimeter.

If you observe resistance that is extremely low or extremely high, the problem is most likely with the heating element. If it shows a normal resistance value, the issue is with the circuit board.

To test the voltage, simply place a voltmeter on the heater terminals. If the voltage is higher than this, the problem may lie with the heater board. To test for voltage, you can also test the neutral wire on the spa board.

A good voltage level should be between 110 and 120V. If the voltage reading falls outside of these ranges, it is likely that the problem is with the heater board and not the heater itself.

When performing this task, be sure to use a good set of wrenches. Be sure not to twist or bend the terminal hex. If you do, it might crack the epoxy seal and allow water to seep into the hot tub.

Be careful not to twist the terminal nut, as this will cause it to fail. If you notice any sparks coming from the heater terminals, turn off the hot tub immediately and check the heater element.


If you are unsure how to check the heating element, take the spa to a repair shop. This task can cost between $100 and $300.

Remember that heater replacement is an expensive project, so it is best to hire a professional to do it.

Checking the heat element is not easy, and it requires specialized knowledge in the field.

However, it is worth the effort if you can’t afford to replace the entire unit.