Solar Heating Controllers   Controller Symptom  Possible Cause (s) Corrective Action Control will not turn pump (or pool valve) on or off in automatic mode but turns on in manual mode. 1. Defective temperature sensor 2. Defective control 3. Open/short in sensor wiring 4. Sensor(s) not properly located 1. Replace defective sensor (s) 2. Replace control 3. Repair / replace wires 4. Relocate sensors Shuts off at the wrong high limit or will not shut off at all. 1. Defective sensor 2. Sensor poorly located 3. Defective control 1. Replace sensor 2. Relocate sensor 3. Replace control Pump runs after dark but eventually shuts off. 1. Defective sensor (s) 2. Sensor poorly located/insulated 1. Replace sensor 2. Relocate sensor/insulate Pump cycles on and off briefly after dark 1. Thermosyphoning 1. Replace / install check valve in feed and return lines. 3-Way pool valve turns continuously (pool or spa) 1. Bad micro switch or micro switch out of alignment. 1. Replace or adjust micro switch 3-Way valve wont turn even in manual mode (pool or spa) 1. Bad micro switch 2. Valve jammed with debris 3. Defective motor 1. Replace bad micro switch 2. Clear obstruction 3. Replace valve Short cycles at high limit (spa) 1. High limit sensor is too far from the spa 1. Locate high limit sensor closer to the spa Return to Solar Repair Page