I really appreciate you offering your input and trying to help. But did you read the whole thread?
I did state that I had never worked on a Baptistry before, and I hadn't. But I'm usually pretty good at figuring things out coming from a controls background.
If I think I can't help I will tell a customer. My only statement to them was I would look at it and see if I see anything obvious. I made no claim of success in fixing the problem nor offered any warranty. I don't advertise as a spa or Baptistry tech, but sometimes good customers ask for help in areas I might not be familiar with. I will try and help if I can. If I totally don't know what's going on I will tell them to get an expert.
The switch, as I posted earlier, was a flow switch and not a pressure switch. It was indeed working and doing what it was supposed to do. If there was no flow, the heater wouldn't energize. So that much I was sure of.
I never got it to trip, and they left it on for quite a while and said it didn't trip for them either. I told them if it did it again, we should look into replacing the heater kit, which is the pump, heater, flow switch, and disconnect.
Also, the heater and pump were protected by GFCI. Breaker for the heater, and receptacle for the pump.