Pentair MiniMax NT Heater Error Codes

Reading, understanding, and diagnosing Pentair MiniMax NT heater error codes are understandably confusing for the typical pool owner. In fact, it can be very difficult for any pool owner regardless of his/her skill set. It is simply the nature of the beast.

Troubleshooting and diagnosing technical issues can be more difficult online. It seems like a catch-22 to me, though. The Internet allows us to have instant access to tons of information right at our fingertips. Still, with all the information available, sometimes it can convolute the information and cause even more confusion. It is very similar to when you are trying to diagnose why your back is hurting. Twenty minutes into reading WebMD and you are halfway to diagnosing yourself with cancer. It can be a very slippery slope.

Diagnosing technical issues on older products is in it’s own league. User manuals and technical documents weren’t as informative for the reader like they are now. Today, manufacturers are more tuned in to their customers’ needs. Although the Pentair MiniMax NT heater was manufactured over a decade ago, we still run into pool owners who still own and love their heater and would prefer to fix the issue than purchase a new one.

As I began my research on the Pentair MiniMax NT error codes, I immediately noticed the lack of resources for this heater. Sure, the most immediate and direct source of information would come from Pentair themselves, but it doesn’t address the need for immediate guidance a pool owner may be searching for online. If you have a Pentair MiniMax NT and are experiencing technical issues, this blog is for you. 

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One of the reasons it is so hard to diagnose technical issues online is because every pool and every heaters are different. Tiny variables in the installation of the heater can attribute to why one thing can fix an error code for one pool owner but not the other. In some instances, the cause of an error code can be unique for the pool owner and their set up. With that in mind, we  gathered as much information and  attempted to include all the different reasons why an error code may present itself. Not every recommended solution will work for every scenario. In the event that our error guide does not cover your particular issue, or simply does not rid your error codes, we recommend contacting Pentair directly at 800-831-7133.

LED Indicators

LEDminiThere are nine lights that can be seen from the front of the control panel. Five are system indicators and four are mode indicators.  If something should go wrong, the lights will aid in troubleshooting the problem.

An additional four lights can be seen after opening the control panel. These four lights are diagnostic indicators for the service technician to troubleshoot the system. Before we dive into the error codes, let’s explore the five system indicators.

I. Power

This light indicates 24VAC power is being supplied to the control circuit. It should remain on at all times. If this fails to light up, so will the remaining indicators. This can mean 2 things:

  1. External power to the heater is disconnected. Check service panel circuit breaker, or fuse.
  2. Transformer has failed.

II. Pressure SW (Water Pressure Switch)

This light indicates the circulating pump is running properly. The light will stay lit when the Spa/Pool Selector switch is on. If it fails to light up, the pump may have lost its prime or your water flow is restricted. Make sure to:

  1. Verify if the pump is primed.
  2. Check water flow restriction. There may be a closed valve or a clogged filter or pump basket.

III. Thermostat

The ‘Thermostat’ light is an indication that your water’s temperature is falling before the set point. This causes your heater to fire in order to maintain the desired water temperature.

IV. Heating

The ‘Heating’ light is on any time the thermostat has signaled a call for heat. This initializes the ignition safety circuit. The heating light is an indication that your unit successfully fired the main burners and will stay on until the water reaches its desired temperature.

V. Service

The ‘Service’ light is off during normal operation of the heater. This light will only come on if a problem with a control has occurred, or when the heater is first firing.

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MiniMax Error Code Guide

The Digital Display Temperature Controller (DDTC) display contains three LEDs with a decimal point between the first and second. This display is also used to display an error code if  there is a failure within the heater control system or a DDTC internal fault. The DDTC will display the actual temperature or the set-point temperature. When the DDTC detects an error, the display will show Exx,  where Exx is the error code of the DDTC fault.   Codes 1 through 9 indicate a “soft lockout”error which means  the heater will resume normal operation and restart immediately after the errors are fixed. Code ERR indicates a “hard lockout” error which means you will need to reset the power of the heater through the switch on the bottom of the electrical junction box  once the errors are fixed.

E01- System Low Voltage

The ‘E01’ error code  indicates system low voltage. What exactly triggers a low voltage? The E01 error can be caused by a few things:

  • Incorrect incoming power
  • Heater connected to the wrong voltage
  • Transformer not outputting the correct voltage

Solutions

Check the voltage going into the heater. If the voltage is correct, the issue may be the transformer.

E02- High Temperature Limit

The ‘E02’ error code  indicates that the high limit sensor has tripped. A “High Limit” is a safety device that opens the electrical circuit and shuts off the heater based on a water temperature set point within the “High Limit Device”.  The MiniMax NT heater contains (2) high limit devices which are located on the main inlet / outlet header. One senses the inlet water temperature and the other senses the outlet water temperature. To verify, you will need to trace the voltage through the sensor loop to find where it is stopping and which sensor could possibly be at fault. Specifically, you will need to check the voltage on either side of the high limit switch.

An abrupt shut off, such as an electrical shortage or lightning, can also trigger the E02 error code.

Solutions

  • Verify the voltage going through high limit sensors. Replace if necessary.
  • Verify if the heater was wired correctly

E03- Thermal Fuse is Open

The E03 error code indicates that the thermal fuse is open. The thermal fuse/cutoff is a safety device that is held together by wax. Upon detection of excessive heat within the inner front panel, the fuse will open the safety circuit causing the shutdown of the heater. It’s main job is to keep the heat source from hurting the heater. In short, if the thermal fuse is open, you may have fire backing up into the heater outside the fire box.

Solutions

  • Examine the thermal fuse. Replace if you see any sign of wear and tear or defect.

E04- Fan Failure

The ‘E04’ error code is an indication that the fan, or blower, has failed. Sometimes the signs are apparent like simply hearing unordinary noises coming from the fan.  Or, sometimes it can be misconceiving. The blower may turn on and the heater may fire up for a few seconds, but will turn back off within a few seconds.

Solutions

A couple of things can trigger the E04 error code that you should check for:

  • A possible bad air flow switch
  • The tube in the air switch (check if it is chewed up or not connected)
  • A bad blower motor

E05- Ignition/ Flame Failure

The ‘E05’ error code indicates that the ignition has failed. In many cases, the heater may fire up and heat for a few minutes, but shorten out. Typically, this is caused by a bad igniter, but not always. This also frequently happens to pool owners who have not fired their heater in months. The E05 error code is a pretty general failure code and could be generated for many reasons.

Solutions

A few different possibilities will cause the E05 code. Make sure you check:

  • Igniter- It’s possible that the igniter is bad or just a little rusty. Try cleaning and restarting the unit. You may need to replace it altogether.
  • Burner assembly- Check for rust debris from the base heat shield louvers. They tend to rust.
  • Bad sensor- Check the sensor to ensure it’s not damaged in any way. Try cleaning and restarting unit. You may need to replace it altogether.
  • Intake/outtake- Check the intake and the outtake venting for obstruction. This will prevent the igniter from starting.
  • Control board- You may want to check the lights on the back of the control board. There are indicator lights in the back of the board that should help you further diagnose the problem. Pentair recommends calling a certified Pentair Service Technician for troubleshooting the board.

E06- Gas Main Valve or Module Failure

Although there is not much information for this error code online and we are currently waiting for an explanation from Pentair themselves, I did find some information in the manual. If you get an E06 error code, you should check:

  • Fuel supply
  • Thermal regulator
  • Correct orifices

** If you see the ‘E06’ error code, we recommend you contact Pentair directly and allow them to troubleshoot the unit with your over the phone.

ERR- ERROR

Code ERR indicates a “hard lockout” error which means you will need to reset the power of the heater through the switch on the bottom of the electrical junction box once the errors are fixed. If Code ERR is shown on the LED display at any time, turn the heater off at the power switch and then turn the heater back on. If the error code is still displayed, call a certified Pentair Service Technician for repair.

We write blogs like this one to help pool owners save as much money as possible. Why pay someone to do something you could have easily done yourself? It makes little sense. What does make sense, though, is not biting off more than you can chew. If for whatever reason you do not feel comfortable doing anything with your unit, don’t. Heaters are  expensive pieces of equipment and sometimes the pool owner can do more harm than good. A good rule is, when in doubt- give Pentair’s technical support a call. They will troubleshoot the heater with you over the phone and help come up with viable solutions.

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109 thoughts on “Pentair MiniMax NT Heater Error Codes

  1. I should have added to “Exact same symptoms on my Minimax 400 DV…” post, i.e.the flashing 88.8 and –.- every 3 to 4 seconds.

    1. Hi I have a minimax nt with the dual knobs on the display and is natural gas. I replaced almost every sensor including mother board and turns on fine. I can hear the blower everything sounds good and then I can see the igniter light up but it won’t fire. I did check the outlet side of the gas valve and noticed the gas does not go higher then 1.5 water column. I did replace the has valve thinking it was the issue and nothing. Also I have the circuit board giving me a the error code tfuse and hi temp and checked the manual and says if those are lit the ignition control module is bad and replace. I did and nothing has changed and heater will not fire up. Any tips

  2. I have the exact same symptoms with my Minimax 400 DV model. I thought it was a control board, bought a new one and replaced, but still have same problem. I see two posts here with same symptoms, but no follow up. Has anyone seen this behavior? I guess I will post over in the forums area and may need to call Pentair.

    1. I did a little digging on this to see if there was any successful troubleshooting and I found something about testing the temp sensor. The “888” you see on the display means the board is doing an internal check during power-up, but it is not going to the next step. Follow this back and forth I found between tech and homeowner, HERE.

  3. I have the same issue. I have a Pentair NT. it was showing a Err Eo4 message. I replace the Fan Run capacitor and the Thermistor still gives the same erro E04. I have cleaned the burners. I see the igniter glow and can hear the gas but it doesn’t fire up. What else I should do?
    Thanks

    1. I just wanted everyone to know that the Pentair Minimax NT will give you the wrong error code. As stated above Err E04 was displayed. I tested the new Fan sensor to to make sure it closed on spin up. I noticed that the Fenwall displayed the 3 flashing light error code for ignition lockout. As soon as I saw that I knew it was either spiders in the orifices or the gas sensor. Pulled the orifices out an big spider nests. Cleaned all 6 and it’s back to working just fine. I guess Spiders like the smell of gas, so even though it is a 2 hour job clean your orifices.

  4. Need some help with NT 400….. first off, my Digital readout only has select portions lit….. this was not much of a problem because I could just check the temp from inside the house. But, it is a problem now, because I can’t read the error code. LOL

    The lights that are lit on the left side, are Power, Pressure and Service. No lights are lit on the right by the buttons.

  5. Hi Matthew
    I have the Pentair Minimax NT. When I turn on the heater the blower turns on, there’s a click after a minute but then the air blowing never gets warm. The only lights on the display that are lit are Power, Pressure and temp, the heating light doesn’t light up. There aren’t any error codes on the display however when I open the panel the diagnostic light is blinking and the chart says “air flow fault” for the particular blink pattern. Any ideas of what could be wrong?

    1. My first guess would be an airflow issue :). It could be as simple as the heater is too sooted and needs a good cleaning to allow for enough air to flow. The more likely cause is a bad air flow switch (key 42), air switch tube, or a bad blower motor(key 5). In section E04 – Fan Failure, we list similar symptoms to yours:

      The ‘E04’ error code is an indication that the fan, or blower, has failed. Sometimes the signs are apparent like simply hearing unordinary noises coming from the fan. Or, sometimes it can be misconceiving. The blower may turn on and the heater may fire up for a few seconds, but will turn back off within a few seconds.

  6. I was cleaning out filter and noticed that after I turned on pool, it said temp was 90 degrees on the heater screen, even though it’s been very cold in California and maybe water temp could be 70ish. I didn’t think nothing of it, and went along my cleaning. I went to go start heater today to jump in jacuzzi and when I turned on system, it said HI… does this mean it could be the thermostat on unit?

  7. I have a Pentair NT. it was showing a Err Eo4 message. I replace the Fan Run capacitor and the Thermistor still gives the same erro E04 what else I should do?
    Thank you,

    1. I have the same issue. I have cleaned the burners. I see the igniter glow and can hear the gas but it doesn’t fire up. Did you get an answer for yours?
      Thanks

  8. i have no error message, but blinking 88.8

    no thermostat light on 🙁 we can adjust the temp but the heater doesn’t come on

  9. I’m experiencing E04. I cannot see any air flow switch on my system it is NT 300 STD N. IS there some kind of diagram that would show me where to look? I don’t think it’s the blower because the unit heats up for a second and hot air comes out the vent but then it cools down so I assume the flame is being shut off but the air still comes out of the vent. It does this 3 times then I get an ignition lockout. Thanks.

  10. I have a Pentair NT. it was showing a Err o4 message. Based on a previous direction I replace the Fan Run capacitor. After the replacement the err message discontinued but the heater continues to not fire. I would expect to to find other error messages but nothing. the heater simply does not fire and not error messages.

    1. The article mentions three possibilities of what could cause E04 code; you may have remedied one, but what about the others:

      A possible bad air flow switch
      The tube in the air switch (check if it is chewed up or not connected)

      A bad blower motor

  11. Hello,

    My display is blinking between 88.8 and “–.-” At the same time as the 88.8 the Service, Spa, Pool and remote LEDs also light up. During the “–.-” the Off, Power and Pressure LEDs are all lit and also stay lit during the 88.8 flash. The flashing is every five seconds. I have replaced the control board thinking that was the problem, but both the old and the new/replacement board are exhibit the same flashing. Pentair Minimax NT DV400

  12. I have an older Minimax NT heater and I don’t have the digital display on it. Just have the lights on the display.
    My heater starts then shuts off within 20 seconds. I replaced the thermistor, both limit sensors and the flow switch all located on the in/out manifold. It still does the same thing. How can I get the error code that the topics above have discussed?

    1. Because your heater is an older model that does not have a digital display, there is no way for you to read error codes. If your heater is that old, it may need a thorough cleaning of soot. You may also want to try contacting the manufacturer Pentair to see if they have a preferred method of troubleshooting for your model.

  13. I’ve been fighting with my Mini max not for a month. I have replaced the igniter, flame sensor and ignition control module. I finally have flames in all of the burners but it goes out after a minute or so. It is now giving an E05 ignition code. The unit is clean, all wires intact, fan works. I’m out of ideas, I’d love to hear some.

    1. The first idea, get a new heater.

      But kidding aside. It sounds like you have done everything I would have suggested. If you have checked all the venting for blockages and heat exchanger for rust, then I am not sure what else you would check. The last part of the E05 section of the article states this:

      Control board- You may want to check the lights on the back of the control board. There are indicator lights in the back of the board that should help you further diagnose the problem. Pentair recommends calling a certified Pentair Service Technician for troubleshooting the board.

      As much as it pains us DIY-ers, sometimes calling in a pro is the only thing left to do.

  14. I should add that the temp outside has dipped below freezing for the last 2 days. Not sure if that could play into this … ?

  15. Mine says “ LO “ and doesn’t turn on. The pressure switch light is on and so is the power led. No other system indicator leds are lit. Any suggestions? Thanks!

  16. I have a 10 year old MiniMax NT Series that will not engage. There is an error msg light of e08. I have looked in the manual and also online and cannot find that message indicator.

    Has anyone come across the same situation.

    1. I tried to search for the E08 too and came up dry. I eventually called Pentair, and they state that it is not a valid code. The codes numbers stopped after E06. The tech I spoke to sad, you main have a display issue, along with a deeper issue preventing your heater from turning on. They would have to know at what point does your stall out in the process of starting to figure out the issue.

      He also said, you should give them a call and they would be able help you figure out the problem over the phone.

  17. After not using our Minimax for a season and replacing our pool pump, I received the Er04 code. The power, thermostat, etc lights were on but not the heater light. The fan was on and blowing air out of the top of the unit. I went and checked the manual and read that if the unit had not been in use for a while that it is common for it not to ignite. By the time I had finished reading that, the system had ignited and the spa was heating. We used it the next evening and it fired up properly. After a couple hours when I went to turn it off, I noticed the led already said off, though the spa was hot as expected. The next day, it wouldn’t ignite and ER04. Now, on my pentair, the panel says ER04 = Bad ignition (and not fan failure) Any idea of what I should do?

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