I have a '97 Sundance Optima, 220v, 50A, two pumps, blower and secondary control panel. My problems started last season with just the temperature controls. You could adjust the temp up but not down. It was if the down temp button was inop. Afterwards the temp would re-adjust itself down to 80deg withinh a couple of hours. If I would turn off the spa for awhile it would work ok for about five minutes and then revert back to previous condition. I learned to live with this and enjoyed my spa all season. This year the story has changed. I cleaned and filled spa as normal but now my controls are even worse. At first it was just the opposite of last year, temp adjust down but not up. That didn't last long, now I can't adjust temp, cycles or display. It was previously set at 99deg and that is where it went to at first, but it soon started to drop. The pump cycle comes on as well as the heater and I can turn on the pumps manually as well as the light and blower. Is the Senrty 850 control panel bad or could it be somewhere in the main board. I feel that it is probaly the control but don't want gamble with that kind of money.
Thanks

First, the control panel is the main board. The topside is just an interface to the main board (control panel). The topside is dead. If you have the dual display, try to disconnect just the secondary display and see if the problem goes away. If both displays are the same, and the problem still exists, reattach the second display and disconnect the first one. That will narrow down which display is faulty, and you can run just fine that way.