Mastertemp 400 - Trouble starting after rain

Aweb

New member
Nov 22, 2018
1
Dallas, Texas
Hi all,

I've got a Pentair Mastertemp 400, and similar to this thread my heater has trouble starting after the rain. The blower comes on, it ignites and heats for 2-3 seconds, and then turns off. This repeats 3 times until it gives up and the "service heater" light comes on. If I turn it off and back on it'll start the "3 attempt" cycle again. Usually after a total of 5 attempts it'll light and remain on, functioning as normal until the next rain.

At this point I've replaced the manifold bypass valve, the high limit switch, the thermal regulator, and the Automatic Gas Shutoff switch (all for other failures), but this behavior hasn't changed. It's as though something is getting wet and after heating a bit the wet area drys up and it works again, but for the life of me I can't find anything that seems to be an obvious cause. Any suggestions?
 

Tosier

New member
May 23, 2020
1
Dallas
Hi all,

I've got a Pentair Mastertemp 400, and similar to this thread my heater has trouble starting after the rain. The blower comes on, it ignites and heats for 2-3 seconds, and then turns off. This repeats 3 times until it gives up and the "service heater" light comes on. If I turn it off and back on it'll start the "3 attempt" cycle again. Usually after a total of 5 attempts it'll light and remain on, functioning as normal until the next rain.

At this point I've replaced the manifold bypass valve, the high limit switch, the thermal regulator, and the Automatic Gas Shutoff switch (all for other failures), but this behavior hasn't changed. It's as though something is getting wet and after heating a bit the wet area drys up and it works again, but for the life of me I can't find anything that seems to be an obvious cause. Any suggestions?
I’m also in Dallas and have been battling this issue also today (after last nights rain). I checked my baskets and backed washed my filter to make sure I had good water flow. Didn’t solve my problem. I looked for led lights on the back of the control board. None. I tried turning the power on and off. No fix. I noticed that the ignition control module would flash 3 times (this different that the led lights on the control board-this light is on the ignition module and flashed a certain number of times depending on the error) and that this was an ignition lockout.

Googled around and read about how the ignition control module needs a really good ground. I undid the those grounds, cleaned the terminals and put the grounds back on. I pushed on the ground wire from my heater that literally goes into the ground and it actually moved into the earth some. Tried the heater and now it works. Not sure what changed but my hypothesis is that all of the rain we had last night made my ground path bad somewhere and that made my ignition control module finicky such that it turned itself off. Maybe the grounds for your ignition control module are good enough for when it’s dry out but cause problems when it has rained.