Incorrect temp reading on Jandy LX heater...HELP!

mojo jojo

Mar 16, 2017
Huntington Beach, CA
I have a 12 year old Jandy LX heater and have had very good luck with it until recently. When I fired it up for the first time this year, the temperature reading was 84 degrees Fahrenheit. I could tell it was wrong by putting my foot in the pool so I checked the floating thermometer and it read closer to 60 degrees.
I cranked the desired setting to 104 (that's as high as it will go) and although the heater seemed to work fine, my pool is now around 75 and I can't get it any warmer because the thermometer still reads 104.
I like it around 85 degrees.

Have any of you experienced this issue? Any help would be appreciated.


TFP Expert
Mar 2, 2011
Check resistance of thermistor. It should follow the resistance given by a 10k thermistor chart.


TFP Expert
In The Industry
Jul 6, 2011
Is the heater running/flames on, when it jumps to 111? If so then it sounds like a water flow or bypass issue. If it's jumping to 111 and you don't have any flames burning, then it could be a bad temperature control.

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