Mastertemp 400


New member
Jan 24, 2021
Carlsbad, CA
We moved into a new home with a pool/spa. It has a pentair mastertemp 400 heater I believe the pool was built in 2013 so the heater may be 7-8 years old. It has been working fine for the spa about 1-2 times a week since we moved in at the end of July, we don't heat the pool. Tonight I turned on the spa for our end of week soak, and after dinner I checked the temp and it wasn't heating, the spa was cycling just fine.

I checked the equipment and both the pool and spa LED were lit, the heating led as off and the display showed the current temp (61 degrees). I turned the equipment on and off, and I could not hear the heater fire up. I checked the heater panel and both green LEDs were still lit, but the display was now blank and no other LEDs were lit. I pressed the heater off button on the control panel, but nothing happened. I tried pressing the pool and spa buttons, but the two green LEDs just stayed lit. Finally I followed the troubleshooting flow chart in the manual and since I don't get any service LEDs the flow chart ends telling me to replace the control board.

Has anyone seen this specific behavior? How much does it cost to have a control board replaced?

Thanks in advance,

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