My 1998 Spa from Sam's Club was working fine. I turned down the temp because it wouldn't get used for a week. When I went to use it I turned up the temp and when I came back a couple hours later the GFI was tripped. I unplugged the heater cord and it would run without the heater. Replaced the $100 heater element. That is what it was last year when the same thing happened. GFI still trips instantly when I plug in the heater cord. Help!

Is there anything else wired into the heater cord like a pressure switch or high limit?

It's an Aquatherm vertical can type heater with the spiral element. There is the 2 wire cord for the pressure switch that is seprate but goes in the same hole in the base of the heater. Thanks

It's possible that your pressure switch is causing the problem Start the spa up with the wires disconnected from your pressure switch. Once the water is moving, jump them to allow the heater to come on and see if it still trips the breaker.

If it does you'll have to move to the control pack. Does this thing have a circuit board or is an air switch style pack? You could have a relay or some other component in your heater circuit that is shorting.

It has an aluminum box with a circuit board, fuses, lots of wires, and relays inside. It kicks out the GFI even with the heater thermostat turned down and the pressure switch unplugged. Soon as i plug in that heater cord- Click.

Check for a short along the cord and at the heater itself. Also check your GFCI wiring with this thread.