my rheem performance platinum overheats, even when turned off. I have had a tech check it for several hours, with no problems found using wiring diagram. Even with the digital control turned off the service wires still pull 3 amps, and continues to slowly heat until the emergency cut off turns it off. Rheem has sent all new parts except the heating elements and the lower sensor. The only way to kill the heater is to turn off the breaker.What is wrong?