Breaker trips within 10 seconds vita spa LC500

I have a vita LC500C/LC700C model. The main breaker trips 10 seconds after it's reset. I've tried unplugging the motors, and all the control lines, the only thing that changes the situation is unplugging the control panel. When i unplug the control panel the breaker doesn't trip. I bought a new control panel, but it does the same thing. help ?

Have you tried connecting everything back to the way it was and then just disconnect the heater by itself and see if it trips. If not then the heater has a short and needs to be replaced. If a spa component is causing the GFCI to trip it is usually the heater.