I am having an issue with my Pentair Master Temp 400 pool heater. I am thinking something is wrong with the heat sensor of some sort. The deal is when ever it is at all a little wet outside the heater does not operate normally. The temperature gauge will fluctuate erratically or just think it is a different temperature all together. Today it sprinkled and when I turned on the hot tub it heated for a while but then shut off. I found that when I cycled the heater it kept saying 28 and when I put it the pool back to pool mode it dropped to 24 so I am assuming it thinks the pool water is 24 degrees and will not ignite the heater. Anyways what part should I be looking at? I looked at the schematic but I can't seem to figure out which one I should be thinking about replacing. After it dries out it always seems to operate normally but it aggravates me to no end when it doesn't. Thanks in advance.