Question about Pentair Mastertemp Pool & Spa Heater Dual Electronic Ignition 400,000 Btu Lonox Propane 460737

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Master temp 400 with E05 error message, already replaced stack flue sensor, thermistor, and igniter. Any suggestions?

Already replaced stack flue sensor, thermistor, and igniter on my 4 year old Mastertemp 400 heater. Still get the same result...kicks on, ignites, heats for about 15 seconds then shuts off and display says E05. Any suggestions that don't involve calling out my pool tech for a $175 service call?

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Eo5 is exaust temperature if exhast gets above 475 degrees it will shut down the heater. check inside combustion chamber for evidence of rodents they build a nest down in the fire cone and around he heat exchanger this will cause high temos and set the eo5 code.
you can depress pool on and spa on for 10 seconds and display will read the exhaust temp , if it get itno the high 400,s you have a problem in there and must be taken apart and inspected

Posted on Jun 24, 2014

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I have the same exact problem with this unit. Obviously getting gas to the unit, because it runs and pumps out some serious heat for a short time, but then kicks off. Did anyone ever figure this out or did you buy a new heater? :-)

Posted on Aug 01, 2012

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I have had the same problem with my '400' since it was new. I contacted the manufacturer and got the run around. I have been trying to get this resolved and now, a year and a half later, have decided to buy a different heater. Anyone want to buy a hardly used Pentair 400?

Posted on Sep 23, 2013

  • Scott Corey-reid Apr 16, 2014

    check the heat exchanger it its calcified. inspect thermal regulator and internal bypass


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Posted on Jan 02, 2017

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SOURCE: Pentair mastertemp 200 will work for a while and

If you are firing, and then going off and getting an E05, your igniter is to blame. It may be glowing but it's getting weak. The diagnostic goes further but that is usually the fix. with inactivity, the igniter is always to blame. You really need to fire it off weekly to make it reliable.

Posted on Feb 25, 2011

  • 1 Answer

SOURCE: getting a E05 code on my Mastertemp pentair

I have same problem. Mechanic not sure what to do. May need a new board.

Posted on Jul 31, 2010

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SOURCE: I have a Pentair Mastertemp 250 pool heater with

This is an ignition flame falure code. Could be you don't have gas getting to the pilot, no spark to ignite the pilot or your ignition is not reading the flame. Sorry to say but it's probally time to get the pool guy out to look at it. Good luck.

Posted on Apr 15, 2010

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SOURCE: Have a Pentair MasterTemp 400

Thank you for posting your question here on

Error code E05 can be caused by many failures in several places. The owner's manual has a decent flow chart in it to help diagnose where the trouble lies. You will find it on page 43 here...

Identifying problems with an electronically controlled pool heater is not a job for most homeowners without training and/or experience with this type of equipment. If you are unsure how to proceed no amount of tips from a site like this will replace experience. You may want to consider hiring a professional to look at your heater.

If you decide to pursue the repairs and need additional support please post as specific a question as you can as a comment to this reply.

If this answer does not fix your problem, please comment with additional details prior to rating the answer. You may also contact me thru our website at Positive feedback is appreciated once your problem is solved!

Posted on Mar 30, 2011

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