G'day,
We just had 5 days of terrific storms here in Northern New South Wales, (Australia) and when the power came back on (after being out for 3 days!) The spa GFCI kept tripping immediately. I fiddled around trying things and found that if I removed a terminal from the heater connection in the control box, everything else works OK (circulating pump, lights, jets, ozone)
I tested the resistance across the terminals of the heater blade connectors and it reads 39ohms. The voltage at the heater terminals on the control panel reads 230v.
I had originally called my local (not so local actually) Hot Spring Dealer (before doing the resistance test) and they reckoned that the heater was the problem. SO I proceeded to take the thing apart, removing the end caps and checking it out, thinking I didn't have anything to lose. Everything looks good throughout, no corrosion, or signs of shorting or anything. Now I'm wondering if the heater is ok and something else is causing the problem? Any suggestions of what to try next would be gratefully received. Thanks

Check the ohms of the heater between the black terminal and green ground terminal. Should get 0 or 'open line'. If you get any other value then the heater is bad. If it is bad you can fly me down there and I'll fix it for you! No really, you would just need to replace it.