Mastertemp 400 not working


New member
Apr 19, 2019
Murrells Inlet, SC
Currently having an issue with my heater. It was running fine last night, went up to 100 degrees, but today it won't heat. When I turn it on, the ignitor kicks on, then immediately turns off. I can hear a subtle beeping and the service heater light comes on. There is no water flow issue as water is flowing into the spa as usual, it is just cold. There are no lights on the back of the board that indicate what part is causing the issue. However, the diagnostic indicator on the fenwal blinks 3 times indicating ignition lockout. The heater is 3 years old and I have not had any problems until now. Anyone have any ideas?


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