Pentair Mastertemp 250 Troubleshooting [11 Easy Solutions]

The common Pentair Mastertemp 250 problems that users often face are the heater not igniting or not turning on and the heater not heating at all. Plus, the heater going out frequently, air flow issue, cycling on/off, display not working, heating light blinking, and heater turning on by itself are also the troubles from which the users frequently struggle.

However, in today’s Pentair Mastertemp 250 troubleshooting guide, we will explore the reasons behind all these issues and give you easy solutions to each problem. So, let’s go on reading…

Pentair Mastertemp 250 Troubleshooting Guide [11 Easy Solutions]

Here are all the issues’ reasons explained with possible simple solutions:

1. Pentair Mastertemp Not Igniting 

Pentair Mastertemp not igniting issue has bothered many users over the years. If you’re also one of them, then you need to know the reasons behind Pentair Mastertemp not igniting. Your Pentair Mastertemp 250 won’t ignite because of:

  • Lower gas supply, 
  • blocked filter
  • defective gas valves, gas supply valves, or plumber valves 
  • Faulty transformer 
  • bad igniter
  • incorrect thermostat temperature setting 


  • You can adjust the gas supply according to the manual to resolve this problem. 
  • Clear out all the clogs and dust to unblock the filter.
  • Replace all kinds of defective valves.
  • Purchase a new transformer and install it. 
  • Replace the bad igniter with a new one. 
  • Check out the thermostat setting from the manual and set it according to that. 

2. Pentair Mastertemp Not Heating

Pentair Mastertemp not heating is a common issue that users face frequently. There are different reasons behind this as well. Your Pentair Mastertemp 250 is not heating due to:

  • Faulty or damaged temperature sensor
  • Wrong thermostat temperature setting
  • Blocked filter
  • Malfunction ignition system or heating element
  • The trouble with the internal bypass system


  • You have to repair or replace the damaged or faulty temperature sensor based on their conditions. 
  • Change the thermostat settings according to the manual. 
  • Take out the things that are blocking the filter. 
  • Look for the specific portion where the malfunction occurs and resolve it by replacing or repairing the parts. 
  • To fix internal bypass system trouble, consult a professional. 

3. Pentair Won’t Turn On

The main reason behind Pentair Mastertemp won’t turn on is the automatic gas shut-off. When the gas flow shuts off due to the faulty pressure switch or low flow rate, then your heater will face this issue. 


If you want to fix this issue, then you need to check out the water flow rate and make sure it is adjusted properly. Keep the water temperature under 60 degrees. Purchase a new high limit switch and replace it with the old one. 

4. Heater Keeps Shutting Off

Pentair Mastertemp 250 keeps shutting off because the airflow switch is not closed. It’ll take merely a minute or two to start the system with perfect airflow in a Pentair heater. But when the airflow switch remains on even after starting the system, your heater will keep shutting off. 


To solve this problem, you need to keep the airflow switch close first. When the system gets the right airflow to start the system, close the airflow switch right away. Then your heater won’t keep shutting off. 

5. Air Flow Fault

Pentair Mastertemp 250 air flow fault occurs due to the excessive exhaust temperature detected by the flue stack sensor. It will open the stack flue sensor, and therefore your Pentair Mastertemp heater may shut off entirely. 


Turn off your heater and see if the thermal regulator has been damaged or bad. If it has gone bad or damaged, then try repairing or replacing it based on the condition. This will solve the airflow fault of the Pentair heater. 

6. Cycles On And Off

When the sensors are damaged by the improper flow of gas from the system, Pentair Mastertemp 250 heater cycles on and off can happen. Even when the cycle valve is broken, this problem can occur to your heater. 


Check the pressure flowing of the gas in your system and compare it with the preferred limit. If there is any difference, make sure that the gas pressure remains between the prescribed limit. 

7. Heating Light Blinking

Pentair Mastertemp 250 heating light blinking means the heating light is not getting enough power or has gone bad. When the power panel can’t provide the required power to the heating light, then it starts blinking to send a warning. 


To deal with this blinking light, you need to check the connection and make sure the heater is getting enough power. If this doesn’t solve the issue, you have to replace the light. 

8. Heater Turns On By Itself

When Pentair Mastertemp 250 turns on by itself, it refers to the fact that the water pressure switch is open as it is open so it is indicating the heater to turn on and therefore it is turning itself on. 


You can easily fix this problem by rotating the water pressure switch. When the switch gets closed, it will provide no indication and therefore it won’t turn on by itself. 

9. Display Not Working

Your Pentair Mastertemp display not working is a major issue because you won’t be able to put any command on it when the display isn’t working. You won’t get any other error code when this problem occurs. 


If the display isn’t damaged, it’ll only take a reboot to get back your display. But if the display is damaged or gone bad, you need to replace it with a new one to fix this issue. 

10. Ignition Lockout

If the high-temperature switch is on in your heater, then Pentair Mastertemp 250 ignition lockout will happen. When the ignition lockout occurs, your Pentair Mastertemp 250 not igniting issue will appear. 


To avoid this ignition lockout, you need to keep the high-temperature switch off. There will be no ignition lockout, and the Pentair Mastertemp 250 not igniting issue won’t appear. 

11. Leaking Water

Pentair Mastertemp 250 leaking water refers to the openness of the water sensor for temperature. If your water temperature sensor gets faulty by any means, then it will start leaking water. 


To fix this issue, you need to close the water sensor for temperature first. Then you need to check out the condition of the sensor and find out if it is in optimum condition or not. If not, then get it repaired or replaced the right way. 


Why Won’t My Pentair Mastertemp 250 Fire? 

Your Pentair Mastertemp 250 won’t fire due to the dirty filter of your swimming pool. This is the most common cause behind Pentair Mastertemp not firing. A dirty pool filter will restrict the flow of the water forcibly and the heater won’t be able to fire. So, clean the pool filter to fix it.

How can you reset your Pentair pool heater? 

To reset your Pentair heater, you need to turn the power down to the heater for 10 seconds at least. Then, you need to reset the heater from settings. After that, you need to turn on your heater and it will reset all the functions to default. 

How do I fix the power issue of my Pentair heater?

In order to fix the power issue of your Pentair heater, you need to check the connection out first and ensure that the heater is getting enough power. If it still doesn’t fix the issue, then you need to open up the heater to find any damaged parts inside it and repair or replace it. 

Why is your Pentair heater blowing cold air? 

When the heater’s filter is clogged then it can lead to the heater blowing cold air. Replacing the filter with a new one doesn’t solve this issue. Because the dust and debris reach to the unit and they stay there even if you change the filter. So, you need to clean the unit first and then the filter to get warm air. 

Final Verdict

Hopefully, this article was able to help you sort your problem out and show you the right solution for it as well. In that case, it would be better if you strictly follow our guidelines and use our methods to fix your trouble. Because only then you will be able to sort your Pentair Mastertemp 250 Troubleshooting. 

But if this article and the methods in it don’t show you the path to find the problem and solution, then let us know in the comment section about your issue in detail. We would be happy to help you solve your problem in no time.

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