Slycooper91

Hi I have a 2000 hotsprings jetsetter model j that I'm attempting to repair. So far I replaced the heater circulation pump which got the hot tub working after 2 or 3 years of sitting for about 5 days after which it started to blow the gfci plug. I ohm'd the heater and it reads 10.8 ohms. When I reset the gfci it starts up Until it hits the heater and trips. With the heater unplugged it operated normally. What could cause the problem in the heater if the resistance is In spec?