My Max-E-Them heater runs for a few hours then the service heater light comes on. If I turn off the heater and wait a couple hours, the heater will come back on. Also, the effectiveness of the heater decreases the longer it is on. For example, the temperature in the pool raises from 70 to 80 degrees in approximately 1 hour, but from 80 to 81 may take one hour, the I get the service heater light. My pool flow is normal, and there are no rat nests in the heater. I borrowed a neighbors old board and swapped it out, and the behavior did not change,