I have the same problem on my starite SN200NA. Display always reads 125-126 but pool water is 65-72. I pulled the thermistor and tested it with an ohm meter. It does vary as the temperature changes (resistance goes down as heat goes up) but I'm not sure what the ohm range should be. Does anyone know what this range should be? I called sta-rite/pentair and they referred me to a local dealer who wasn't any help.
It may just be time to replace the control board as others have mentioned. 5 of the LED segments are burned out on mine so I have to guess the error code and temperature it is displaying. That's just a minor inconvenience I'd put up with if I knew I could fix it with a $60 thermistor instead of a $300 control board.
