Pentair Mastertemp fails after it rains

avolfson

New member
Jul 11, 2020
3
NJ
Hi all, I know this has been discussed in past, but I don't see a resolution in any of the previous posts.

My 6 year old Pentair MasterTemp 400HD does not heat after it rains. Blower turns on, heater kicks on and starts working but then shuts off after a few seconds. It then does this 2 more times and just shuts off. Service light goes on. None of the lights behind the panel are lit (no error code and no specific component fault).... Any advice? Thank you.
 

avolfson

New member
Jul 11, 2020
3
NJ
Thanks. I kept doing this for about 20 minutes and eventually it stayed on. I wonder if some part somewhere gets wet and senses what it should't. Will look at you suggestion. Thanks again.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
17,222
Tucson, AZ
I tested my flame sense current on the Fenwal and it would barely get to the minimum 2uA. Then I added the additional grounding wire as explained in that Wiki and the flame sense current immediately went back to the normal operating value. Some people get mice and vermin making nests in there and destroying wires, etc. So if you can test your flame sense current when it’s trying to fire, that will be a good indication of a bad ground.