I have a sundance Altimar 2001 model with Sentry 850 system. I noticed that the circuit breaker had tripped so I reset it. The LCD said FLO (steady, not flashing) and the water was at 105 degrees. The thermostat was set at 97 degrees. If I cycle the breaker I can operate the jets and heater controls before the FLO error sets. If I turn the heater up to where it turns on the circulation pump operates fine, however when the temp is reached the heater turns off and the circ pump runs for a couple minutes and then turns off. I checked the power to the pump and none is being directed by the pcb at that time. Normally the circ pump will run all the time but that is not the case now. I think that is the reason for the FLO message but not sure what is causing it. Also, each day I come home from work, pump 2 is on and running for who knows how long and the only way to turn it off is to trip the breaker.

I have checked the FLOW sensor and it shows continuity when the pump is on, and shows open with the pump off which leads me to believe that it is working properly. Let me know if I am wrong.

Does anyone have any suggestions on how to further diagnose the problem? I had a tech out but I don't have any confidence in his abilities after watching him work.

The circuit board is a sundance 6600-056. Thanks for any help you can provide.

I'm experiencing the same problem. The #2 pump turns on by itself randomly. sometimes for a few seconds, sometimes for an hour. I tried resetting the breaker, but now the pump won't turn off at all from the control panel and remains on until I turn the breaker off. It also heats the tub up to max at 104 even though it's set at 96. I'm thinking either the control panel or the circuit board is shot. The circulation pump works fine by the controls.
thanks for your help in advance.