Pentair Heater Not Turning On [7 Easy Fixes]

There can be many possible reasons behind your Pentair heater not turning on. A dirty filter-tripped safety switch, low voltage, defective pressure sensor, low water flow, dirty heat exchanger, and bad control board can all cause your heater to not start. 

Read our Pentair heater troubleshooting guide and fix your heater ASAP.

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Pentair Heater Not Turning On [7 Easy Fixes]

What to do when the heater won’t turn on? In this section, we will look over the possible causes of your Pentair heater not turning on in more detail as well as provide you with simple solutions.

1. Dirty Filter

Checking your filter is the ideal first step in resolving any power issues, regardless of the type of pool heater you have. This is due to the fact that your pool heater is reliant on a constant supply of water.

It will most likely not turn on at all if it does not receive enough water at a high enough pressure. And if it does, it will most likely shut down immediately.


You need to keep your pool filter clean and clog-free to keep it running smoothly. To clean up your pool filter, you need to take the cover off. You should be able to spot 4 elements. Take out the elements.

Clean out all the elements with a hose. After all the dirt has been washed out, reassemble the elements and reseal the pool filter with its cover.

2. Tripped Safety Switch

The safety switches are there to save your unit from damage. Whenever they detect something wrong with the pool heater, these switches trip and cut the power to the heater.

Automatic gas shutoff, high limit switch, pressure switch, and airflow switch are safety switches that can trip for various reasons.


You will most likely get an error code when any of these safety switches trip. The Pentair MasterTemp service heater light may turn on and the LED on the back of your control panel may light up.

Each LED specifically indicates a safety switch that is on. You need to inspect why the switch has tripped and reset it. Your heater should start up after you have reset the safety switch.

3. Low Voltage

If the breaker isn’t providing enough electricity to your pool heat pump, it won’t turn on at all. Lack of adequate voltage supply may be causing your heater to not startup. 


Your electrical outlet may be of less voltage than needed. But if the heat pump used to operate fine when connected to the same outlet but no longer does, the issue could be a faulty electrical connection. Take care of the following things.

  • Make sure the heat pump is getting enough power (usually 24 volts or 12 volts depending on model)
  • Look for any breaks or loose connections in the wiring.
  • Check for corrosion at the wiring terminals.

4. Defective Pressure Gauge

A faulty pressure gauge prevents your pump from identifying water flow, causing it to shut down. 


You need to replace the pressure gauge. Order a pressure gauge to have it on hand to replace the broken pressure gauge. Follow the instructions below:

Step 1: Make sure to turn off the pump. Also, shut down power at the circuit breaker to the pump for maximum safety.

Step 2: Next, you will have to relieve the pressure built up in the filter during operation. To relieve pressure, turn the relief valve on top of the filter counterclockwise. Water may spray out initially as you see the pressure or the pressure gauge go to zero psi.

Step 3: Twist the gauge off in a counterclockwise direction. You can try using an open-end wrench on the brass nut at the gauge’s base if it won’t turn freely.

Put two to three layers of Palmer’s Teflon tape on the threads of the new pressure gauge. Wrapping in a clockwise direction will allow the tape to stay on when you screw the new gauge in place.

Step 4: Thread the pressure gauge into the air relief valve in a clockwise direction. Use an open-end wrench to tighten the last half-turn. Do not over tighten.

Step 5: Turn on the power to the pump at the breaker box. Close the air relief valve when a continuous stream of water flows out.

Check the pressure reading on the pressure gauge. It should read about 10 to 15 PSI. Make sure the start arrow is aligned with the current reading by turning the front dial as needed.

5. Low Water Flow

An obstruction in your pool system can prevent your heater from turning on due to limited water flow.


Ensure that your pool filter is clean. Empty the baskets. Make sure the pump is sending enough water through the system.

6. Dirty Heat Exchanger

This is the portion of the pool heater that transports heat from the inside of the unit to the water in your pool. If it’s dusty or corroded, though, it might cause the unit to shut down and occasionally even prevent it from turning on.


You need to clean your heat exchanger and see if the issue is solved. In case it persists, you need to replace the heat exchanger.

7. Bad Control Board

The control board of your heater can be compared to the motherboard of a desktop. It is essential for the heater. A defective control board can be why your heater refuses to turn on.


Ask your heater manufacturers for help. They can send you a replacement control board. If you have a good degree of experience with electrical appliances, you can DIY replace the control board. Otherwise, we recommend you contact a professional.


How to turn on the Pentair heater?

First, make sure that you press the MENU and your heater panel is in auto-mode. Go down to HEAT, and press SELECT to set the pool temperature. Press SELECT again, and set the setting to HEATER. Your heater should be on.

Why is there no power to my pool pump?

Whenever your pool pump won’t come on, the first place to search is for any electrical problems, such as a faulty breaker, wiring, or capacitor. If your pump is automatic, make sure it’s turned on in the first place by checking the timer.

What happens if air gets in the pool pump?

If the pool pump is drawing air, the priming may be lost. It’s also possible for the pool pump to overheat or cavitate.

How do I bleed the air from my pool pump?

To clear the air from the pool lines, start by closing all of the line valves. Keep opening the valves to add air into the pump while it is running until the pump has sucked out all of the air.

Should I backwash after vacuuming the pool?

Yes, we suggest backwashing your pool after vacuuming it. This enables the filter to eject any dirt or debris that has been vacuumed up. After backwashing, remember to set your filter to “rinse” for 30 seconds.


Hopefully, you have got the solution to your query, “Why is my Pentair heater not working?”.

If you are in confusion about your Pentair pool heater troubles, you can let us know by leaving a comment below. We will come to you shortly with a possible solution.

About David

David is a man who loves doing research and finding out the best solution to any type of heating appliance issues like heaters and fireplaces. Whenever he finds the perfect solutions to any issues of heating appliances after doing in-depth research, he loves to share them with his readers. In fact, his aim is to help his readers to fix the issues with their heating appliances easily.More about us .

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