Have a circa 2003 ProForm "Orbit", model #PFSG51030.
Control Panel: Balboa ICON 10, is presently wired for 110v
On circuit board, the Heater Mode Selector, J23, is set for 20 amps (not the alternate 50a).

All appears to be working properly except for one thing: Although the digital temp display shows 104, the real temperature, measured by two other thermometers, reads a steady and consistent 100/101. My body also tells me that we're way short of 104. This would seem to require some kind of calibration correction or "control thermistor" (?) replacement. There does not appear to be any additional "top side" adjustment, just a maximum setting for 104.

For years, in my dearly missed old Tiger River spa, my personal preference was to be in for about 10 minutes at a real 105. Would like to be able to get that with this spa, but will be okay to achieve a genuine 104 degrees.

Will appreciate any "warming" thoughts anyone can send this way,
Craig

I have the same issue with 2003 catalina spa the digital topside reading says 104 but the water is really only about 95...Is this the temperature sensor that is poking through the inside fo the tub, or it is just a calibration issue as you mention. Were you able to find out anything on your problem?