I have a Sta-Rite heater model # SR400NA. (Serial # N4 1F03C 018). It is about 10 years old. When trying to use it recently I noticed that the buttons to adjust the temperature would not respond. I had to repeatedly push and/or hold a button in to get it to change.
The next time I tried to use it none of the buttons were responding. It is now "stuck" on. Anytime I turn on the power the heater turns itself on. If I hold the off button it may turn off but, in a few seconds comes back on. The temperature display shows random numbers. One second it will show the correct temperature then change to some other numbers.
I checked for trouble codes on the control board and there are NO lights on. The only light on the board I see lit is the (green) CR25 code. I suspect that the entire control board is bad but, it is a very expensive part and don't want to just guess.