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    Pentair Mastertemp 400 Short Cycle

    Hello, I have a Mastertemp 400 that is short cycling (heats for 30-40 seconds then stops for 30-40 seconds, rinse and repeat). I have replaced the Control Board, HLS, AGS and Stack Flue Sensor. The Thermistor appears to be functioning (reporting correct water temp at the heater display) and...