Mastertemp 400 Short Cycling

dehn0045

Member
Jun 7, 2018
13
LEAGUE CITY
After talking with Pentair I am a little disappointed but not surprised. The guy that I talked to prior to submitting my registration information told me that the heater would be covered for 2 years after the pool was turned over to me by the builder, which wasn't until 12/31/18. Then yesterday the guy that I talked to said that the 2 years started when the gas was hooked up (i.e. installation), which I know happened around 8/11/18. I know that the pool wasn't even filled with water until 9/24/18. I will try them one more time for clarification, but I'm not interested in trying to cheat my way to get a warranty claim covered, but a part of me was hoping that they would consider the circumstances.

The Pentair rep did also suggest the Ignition Control Module because he said that it should only attempt to light 3 times prior to locking out with the service heater light, I have pretty consistently observed 5 attempts (when it fails to light).

Some more troubleshooting today:

Static supply gas pressure: 10 inches
Dynamic supply pressure: 6.5 inches
lower bolt on the tube sheet removed and no liquid drained

Today I started it 3 times and every time it lit on the first attempt and the stack temp heated to about 275 then the heater tripped (about 3-4 minutes of running) and immediately went to re-light. Immediately prior to tripping the supply gas pressure was steady at 6.5 inches. I did notice that the control board did not respond after I turned the heater off and then pressed "Pool On", I had to press it 3 times before the heater booted up, this seemed a little strange.

I am still a little confused which failures should lead to a "service heater" light and which might not. I am assuming that if the flame sensor is going bad that this usually leads to a "service heater" light the first time it trips. I'm still not 100% certain that I tested the common grounding issue properly, maybe my next step will be to get a true rms meter to test the flame sensor. I might also just try swapping out the FENWAL and see if that fixes the problem.
 

JamesW

TFP Expert
Mar 2, 2011
20,821
I did notice that the control board did not respond after I turned the heater off and then pressed "Pool On", I had to press it 3 times before the heater booted up, this seemed a little strange.
Maybe a failing membrane pad or a failing control board. Seems like there are multiple issues.
 

dehn0045

Member
Jun 7, 2018
13
LEAGUE CITY
Thanks @JamesW for all the help. I'm going to proceed with replacing the FENWAL and see if that solves the problem, if not it won't be bad to have a spare on hand anyway. Then go from there, will let you know how it goes.
 
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dehn0045

Member
Jun 7, 2018
13
LEAGUE CITY
I called Pentair back again for clarification on the warranty issue. She said that since it was all part of the builder equipment package that everything gets an extended 3 year warranty, so turns out it is still covered. The tech came out today, I wasn't able to be there with him so I'm not certain about all of what he observed, be he said that he found the membrane pad, control board, and ignition module all were bad and all were replaced under warranty. Makes me wonder what he saw that led to replacing each component, or if it was just a shotgun approach. Either way, I'm pretty confident that will do the trick. If not, I'll be sure to follow up, but for now the case is closed. (Sorry to anyone that followed this thread to the end only to see $500 in components replaced without details on why)
 
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JamesW

TFP Expert
Mar 2, 2011
20,821
the membrane pad, control board, and ignition module all were bad and all were replaced under warranty.
OK, that's what we suspected might be wrong. It's difficult to diagnose multiple issues simultaneously. In any case, I'm glad that you got this resolved. Hopefully, it will work well from now on.
 
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