Help Troubleshooting LXi Heater

[Pro Golfer Mark]

I have Jandy LXi heater and I'm having trouble with the temperature sensor. The actual water temperature is 78. The LCD display on the heater shows the water temperature is 104 which is bad because that is the max water temp and the heater shuts off at that point. I disconnected the two water temperature sensor wires from the PCB and checked the resistance which showed 9.9. This corresponds with a 78 degree temperature reading according to the manual. I then reconnect the wires to the PCB and the LCD temp shows 78. Great! I think I have it fixed. However, within a couple of hours the temperature shows 104 again. I can then disconnect and reconnect the wires and it goes back to 78. I thought maybe the resistance was fluctuating, so I tested the resistance for over a minute and never saw a change. Any other troubleshooting steps I can try without buying parts? If I do buy a part, should I get the temp sensor or the PCB? The heater is hooked up to an aqualink controller which turns it off or on based on another temperature sensor near the filter which is working, is there something I can do to bypass the heater temperature sensor so the heater comes on when requested?

 

[ps0303]

Sounds like you have a bad board. Reading the resistance is the correct way to see if the sensor is working correctly.