Hello all. I am the proud new owner a a very old but nice 1989 Sundance Sentry 605 Marin. Everything works great on the unit except for it seems there may be a thermostat or heater issue. Here is what has happened...

We are wired with 240 and the first day we installed the tub it heated up to it's max temp (104f) without an issue. Since then even in standard mode with the temp gauge maxed out for a whole day it never gets past about 80f. It seems like the heater is indeed working and in fact the previous owner thought the thermostat was broken since the tub got too hot. So is this a temp sensor issue or thermostat issue. Or perhaps a heating element or flow through the heating element problem?

I can't find a repair manual online for the model so any advice you can offer will be most appreciated.

Also a more simple question..The manual says to filter in at least 1 hour cycles for about 6 hours a day, is that right or can it be safely toned down a bit?

Thank you for your time.