Pentair Master Temp 400 - difficulty starting after rain

[cwuffman]

It seems that after any heavy rain the Master Temp 400 tries to fire up and then quickly shuts gas off to burner. The pattern seems to be that after 3 attempts it quits trying and says service necessary. After I manually turn the unit off and then on again it will again try to start 3 times, and usually will be successful on one of these attempts. I am a bit surprised that rain should be a problem since these units are designed to be outdoors. Does anyone know what the interlock device is that is causing the shutdowns?

 

[mrcarcrazy]

I'd take the front cover off and see what isn't happening. getting spark?

http://www.pentairpool.com/pdfs/MasterTempOM.pdf

pg 38

 

[cwuffman]

Sequence is: Blower comes on; short wait, then gas comes on and ignites (you can hear ignition and feel the heat); gas shuts off after 2 or 3 seconds and blower remains on; waits maybe 30 seconds and tries again. After total of 3 attempts, the requires service light comes on and no further attempts are made. I turn heater off and wait 30 seconds, then turn on Spa. Process repeats unless successful, then it stays on as normal. Seems like something is drying out in the short burn times.

 

[mrcarcrazy]

Sequence is: Blower comes on; short wait, then gas comes on and ignites (you can hear ignition and feel the heat); gas shuts off after 2 or 3 seconds and blower remains on; waits maybe 30 seconds and tries again. After total of 3 attempts, the requires service light comes on and no further attempts are made. I turn heater off and wait 30 seconds, then turn on Spa. Process repeats unless successful, then it stays on as normal. Seems like something is drying out in the short burn times.

http://www.troublefreepool.com/threads/9951-Pentair-MasterTemp-400-cycles-on-and-off-in-Spa-mode
http://www.justanswer.com/hvac/3b5hj-pentair-mastertemp-400-work-few-min-cuts.html

couple things to try.

 

[ps0303]

Open it up and inspect all of the wiring to see if anything is bare. Maybe you had a mouse in there eating things. It happens often on these units and the Maxitherms.