I have a 2001 calspa and it kept tripping the breaker in the electrical panel. I have narrowed it down to possibly the heater (my guess). When I remove the 2 wires on the circuit board which feed through the back of the cabinet to the heater and then try to run the spa it does just fine. As soon as I hook the hetater wires back up the breaker trips about 10 seconds later and the display reads SF. Can anyone tell me what the cause of this might be. Is it the heter unit that's bad? Thanks so much for all your help in advance.
Dennis

On a spa that old its quite possible the heater has an internal short. This may allow the heater to continue to function but trip the GFCI. SOunds like you need a heater. You can check continuity of the heater (while its totally disconnected) if there is continuity between either hot terminal and ground or neutral then it needs replacement