Pentair Pool Heater Won’t Ignite [5 Easy Solutions]

Pentair pool heater won’t ignite mainly due to the igniter malfunction, inadequate gas pressure, and faulty gas valve.

Also, the temperature setting in the thermostat is lower than the water temperature, and the pool heater is turned off is another reason why your heater won’t ignite.

Replace the faulty igniter and defective gas valve, and ensure adequate gas pressure in your heater to solve the Pentair pool heater not igniting issue.

Also, make sure that the thermostat’s temperature setting is higher than the water temperature, and that the heater is turned on. 

pentair pool heater won't ignite

So, in the following section, we explained the A-Z detailed causes of each of the above-mentioned issues and their effective solutions.

Keep reading the article, and you will surely learn to fix your Pentair pool heater’s not ignition trouble by yourself.

Pentair Pool Heater Won’t Ignite [5 Easy Solutions]

After powering up or turning on your Pentair pool heater, suddenly, it may fail to ignite mainly for the following reasons.

Note: You can also read how to fix Pentair Mastertemp 400 common problems.

1. Defective Igniter

Igniter malfunction is one of the main reasons for which you may experience a Pentair mastertemp 400 ignition lockout situation. If the igniter doesn’t function properly, the Pentair pool heater fails to ignite. The accountable factors for it are: 

  • Electricity’s high-voltage supply
  • Short circuit
  • Worn-out igniter
  • Too cold igniter
  • Broken igniter
  • Dirty or clogged igniter


When your Pentair pool heater suddenly stops igniting, you should immediately check its igniter. If the faulty igniter is causing this trouble, you should replace it. The other solving ways are:

  • Ensure the adequate voltage supply of electricity and check the short circuit in your electric line
  • Replace the broken or worn-out igniter
  • Make sure your pool heater’s igniter is not too cold, and it is warming up to fire up
  • Properly clean the clogged igniter and remove the igniter dirt or debris build-up

2. Inadequate Gas Pressure

The gas valve inlet’s inappropriate gas pressure is another reason why your Pentair mastertemp 125 won’t ignite. Due to the inadequate gas pressure, the pool heater is not running long enough or failing to ignite. The causes of it are:

  • Faulty gas valve inlet or gas valve inlet is not working
  • Dirty filter
  • Faulty thermostat
  • Low or inadequate gas supply or no fuel to ignite
  • Poor air supply
  • Gas leak
  • Gas stops flowing


Check the gas valve inlet’s gas pressure and make sure your Pentair pool heater has adequate gas pressure. Also, ensure proper venting of your pool heater. The easy ways of solving the above troubles are:

  • Check whether your pool heater’s gas valve inlet is perfectly working or not. If not, replace the defective gas valve
  • Properly clean the dirty or clogged filter
  • Replace the malfunctioning thermostat
  • Make sure the gas supply is sufficient and your heater is getting sufficient fuel to ignite
  • Inspect your heater’s gas leak and repair it immediately
  • Ensure the proper flowing of gas to the heater

3. Faulty Gas Valve

If your pool heater won’t ignite and make a buzzing noise, the defective gas valve is probably creating the issue. When the gas valve solenoid fails to open fully, your pool heater will not light. The factors that cause this trouble are:

  • Wear and tear in the gas valve or its manufacturing defects
  • The gas valve and thermostat’s faulty or incorrect wiring
  • Closed valve
  • The gas valve of your pool heater is in the “Off” position
  • The gas line contains air


When your pool heater attempts to fire up, you should lightly put your fingers on the heater’s gas valve to see whether you can separate the gas valve’s buzzing or chattering. The other solutions are:

  • Replace the manufacturing defective or worn-out gas valve
  • Ensure the correct wiring between your pool heater’s thermostat and gas valve
  • Make sure the gas valves are open
  • Check the gas valve’s position and ensure it is in the “ON” position
  • Ensure there is no air in the gas line

4. Thermostat’s Temperature Setting is Lower Than the Water Temperature

The thermostat’s temperature setting is lower than the pool’s water temperature is another reason why your Pentair mastertemp 125 won’t ignite. Incorrect thermostat temperature settings or faulty thermostats mainly cause this issue.


Inspect your pool heater’s thermostat setting. And ensure that compared to the water temperature, the thermostat’s temperature setting is higher. If the thermostat temperature setting is lower, at first, reset your Pentair pool heater and then set the temperature again.

5. Pool Heater Is Turned Off

Sometimes your pool heater may fail to ignite because it is not in a turned-on situation or you failed to turn it on. The turned-off pool heater will not operate, or it will not ignite.


So before taking major steps to solve your Pentair pool heater not igniting problem, you should first check whether the heater is turned on or not. Ensure that your Pentair pool heater is turned on, and then go for the other solutions as well.


Why does my Pentair pool heater keep shutting off?

Your Pentair pool heater keeps shutting off mainly due to the closed gas valve, overheating pump, dirty filter, the faulty heater, and inadequate water flow.

How do you test a Pentair high limit switch?

You need to run the heater as long as the HLS shuts down the high limit switch. Then inspect the temperature of your pool’s water. 80-degree temperature indicates the premature opening of HLS, and you need to replace it.

What does R14 mean on a Pentair pool heater?

The R14 means the heater’s firmware release on your Pentair pool heater.

How do I unlock my Pentair pool heater?

To unlock your Pentair pool heater, go to the “Menu” and select the “Mode” button. Simultaneously press the Mode buttons and Menu Select, and your heater will become unlocked.

What causes E05 on the Pentair pool heater?

Your Pentair pool heater can display E05 errors due to the low water flow, waterside scaled up exchanger or sooted venting, or faulty fuel delivery exchanger.


Optimistically after going through the above well-explained article now, you know all the major causes for which your Pentair pool heater won’t ignite. If your heater fails to ignite, detect the issue first and then, following our above-mentioned solutions, fix those by yourself. 

Don’t hesitate to comment and let us know if you fail to resolve the problem. We’ll back to you with a fixing way.

About William

William is the founder of He has real life practical skills in fixing smoker & heating appliance issues. He loves to share his knowledge & helps others in fixing their appliances & saving their money. William firmly believes that anyone can repair his or her unit with the correct guidance & knowledge. See more at about us.

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