My 330 has chill plates but the entire system was replaced by the previous owner. I experienced similar issues, the thermostat would power up, but the plates and system itself were not turning on. There is a reset button on mine that is located on the internal unit which is located on the port side of the boat behind the access panel in the aft berth - the small panel with 4 screws, no need to remove the entire panel. I hit the reset button and everything powered up. I also have a breaker for the chill plates in the bilge, but again, not sure if that was factory installed like that - i dont think it was. Just some things to try/consider.