Mastertemp 400 cycling on and off no error codes
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Posted

Hi,

I just replaced my mastertemp 400 natural gas heater, and when turned on via screenlogic for either pool or spa heating the unit cycles on and off firing for approximately one minute, then off (unit still on, mode light lit, heating light blinking) for approximately one minute, then firing again for a minute...., over and over as long as heat is called for. No error lights on the front or rear of the control panel during this time.

What avenue should I be pursuing to troubleshoot this?

Thanks
Chuck Spillman

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Richard's picture
Tech, Pentair
It's more than likely that
Richard's picture
Tech, Pentair
Posted

It's more than likely that the thermal regulator (thermostat) may not be opening in which causes the exhaust temperature to increase to close to 500 degrees, other issues could be either the stack flue sensor is not reading correctly or the main circuit board.

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Hi Richard... Thanks for your
Posted

Hi Richard... Thanks for your reply. Sopme additional information: The old heater was doing this as well, and in troubleshooting it, I discovered the manifold bolts were rusted to the point the heads were impossible to turn... that combined with the age of the old unit (8+ years) contributed to my decision to just replace the entire unit. This unit is literally BRAND NEW. So I am pretty sure nothing is the matter with the unit. Would a failing gas regulator possibly cause this behavior? I have a step down gas regulator probably 20 feet from the unit, and it makes a loud "tick" noise when the heater stops firing.

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Richard's picture
Tech, Pentair
The gas regulator would not
Richard's picture
Tech, Pentair
Posted

The gas regulator would not cause this issue, this would be more in relation to the water chemistry condition and history of chemistry as well. Once a heater fires for at least 10 seconds or so, gas would possibly not be a factor, you may want to call one of our technicians at 1-800-831-7133 for a more detailed conversation to verify the issue.

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Hey guys, to close this out..
Posted

Hey guys, to close this out... replaced the thermal regulator, and that did it.... a lot of other crap in between then and replacing the thermal regulator, but that was original problem. I had a plumber come out and check/replace the regulator (it actually had an issue, but not that would have caused this problem, and thank goodness I had it checked anyway, the failure could have been disastrous), at some point during this process the heater stopped trying to ignite, but it was clear from testing that the igniter itself was bad, so ordered a replacement. That came in and replaced it so the heater started firing again but still short cycling... so I ordered the thermal regulator.... while waiting for it I had a heart attack on my birthday and was in icu for a bit... that really sucked. But when I got home from hospital, the part was waiting and was easy enough for a recuperating 49 year heart attack victim to replace, so I did... and that fixed it. Thanks guys!

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Hey guys, to close this out..
Posted

Hey guys, to close this out... replaced the thermal regulator, and that did it.... a lot of other crap in between then and replacing the thermal regulator, but that was original problem. I had a plumber come out and check/replace the regulator (it actually had an issue, but not that would have caused this problem, and thank goodness I had it checked anyway, the failure could have been disastrous), at some point during this process the heater stopped trying to ignite, but it was clear from testing that the igniter itself was bad, so ordered a replacement. That came in and replaced it so the heater started firing again but still short cycling... so I ordered the thermal regulator.... while waiting for it I had a heart attack on my birthday and was in icu for a bit... that really sucked. But when I got home from hospital, the part was waiting and was easy enough for a recuperating 49 year heart attack victim to replace, so I did... and that fixed it. Thanks guys!

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