Thanks Jersey, the Sn code is not flashing at all it just stays on . The sensor in the tub reads 16.0 and the sensor in the heater reads 15.4 resistance @ 100 f . That's ok according to the chart from balboa . The only other thing it does when power up the screen says 0 then 100 then Sn no pumps or anything will run. Thanks for any help. !!