I have a Sundance spa with a series 750/850 controller, made in 2001. Out of no where it has started to continuously cycle the 2 speed pump on and off, about once every minute. It turns on the pump in low speed, about 10 seconds later it goes to high speed, then after running on high speed it shuts the pump off after about 20 seconds, waits about 1 minute and does this all over again. Have tried turning off the power over night, no help. Temperature sensor seems to be working accurately, flow switch seems OK. I have tried setting he automatic cycles to off and it makes no difference. When the pump kicks in I can not turn it off at the control pane, but when it is off I can manually switch the pump on and off at the control panel. Otherwise the controller seems normal.