I know it's old, but it's been a good one. It's 115 volt, with three external dials on the controler, Heat/Jets, Light, and the Temp. I've disconnected the heater, and the circulation pump, as it had water in it. When I activate the door button, with the left knob on heat, I hear a relay and then it trips the GFI and shuts down. I can turn the left knob to the jets and activate the door switch and it seems to run fine! What do I look for that might be shorting out, that I haven't already taken out of the circuit? The limit switches aren't tripping. Do they shut power off to a relay, to kill the power to the tub? I'm stumped!! It looks like a pain to pull the control box; how do you get the knobs off? I see set screws on the shaft in the box. I think I can get them out, but how in the world do you put them back on when you reinstall it? Thanks for any help.
Robert

If it still trips with the heater unplugged I would open up the control box and look for burnt wires.