Pentair Pool Heater Mastertemp 400 Problems. I suspect that the majority of issues that customers have with the pentair 460736 mastertemp 400 is due to having an inadequate pool system — or they fail to maintain the correct pool chemistry. Everything in my pentair mastertemp heater is working properly except the lcd screen that displays the temp.

My pool heater is a pentair 400. I am having the same problem. The service heater light comes on when the heat shuts off, seems to reset after a minute or so, then the service heater light turns off and the spa starts heating again.