I have a Pentair Mastertemp 400 that is about 3 years old. Recently the spa has not been heating like usual. The spa will only heat to 91 degrees. I checked the temperature setting on the heater and it set to 104. After reading on the forums I believed the culprit could be the thermistor. I replaced it and have the same issue with the new thermistor. The heater seems to believe the temperature is 104 but it’s still only heating to 91. I am not seeing any error codes or lights on the back of the control board. I was considering replacing the thermal regulator but it doesn’t seem like that would effect the temperature reading on the unit. Could this be a faulty control board?
Mastertemp 400 Temperature Issue
- Thread starter jstanley993
- Start date
- Jul 21, 2013
- 53,467
- Pool Size
- 35000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
Welcome to TFP.
You need a multimeter and a 10K resistor.
The temperature sensor is a 10K thermistor. You can measure its resistance with a multimeter.
www.troublefreepool.com
For a test replace the thermistor with a 10K resistor.
If the temperature stays at 76F then you still have a problem with the new thermistor.
If the temperature drops you probably need to check the wiring from the thermistor to the board, and maybe replace the board.
You need a multimeter and a 10K resistor.
The temperature sensor is a 10K thermistor. You can measure its resistance with a multimeter.
Temperature Sensors - Further Reading
www.troublefreepool.com
For a test replace the thermistor with a 10K resistor.
If the temperature stays at 76F then you still have a problem with the new thermistor.
If the temperature drops you probably need to check the wiring from the thermistor to the board, and maybe replace the board.
Thermal regulator is the first thing I would check. Take it out and test run without it