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Something similar to this happened to me last summer. The pumps were possessed and would turn on and off by themselves. The tech knew exactly what the problem was when I described the situation...a bad auxiliary topside control. Replaced same and all is well. Apparently, if moisture gets to the inside of the control, it malfunctions.I found after I shut down the spa for a few hours and started it back up, it would sometimes act normal for quite a while.
Tony, did your lights go on and off and flash, too? Thanks for the reply. I feel better that someone had the same problem and with a Sundance spa, too.