From a 2004 Cal Spa V series manual:
http://calspas.com/downloads/manuals/2004/2004_Spa_Manual.pdf If you've done what they are suggesting then I guess it's possible that all this is controlled by the main control inside the tub and the display is just a display.
Temperature Adjustment (Range 80°F to 104°F)
The display screen will always display the actual water temperature.
Example: The actual water temperature is 100°F, the topside display will read 100.
To display the set temperature, simply depress the Temp pad and the temperature setting will flash on and off on the display panel. While
the display is flashing, each time you depress the Temp pad the set temperature will increase one degree. Allow the display to revert back
to the actual water temperature, then depressing the Temp pad again, allows you to decrease the set temperature by one degree with each
press of the Temp pad.
Standard Heating Mode
Your new spa is equipped with a “Standard Heating Mode” feature that gives you complete control of the heating system.
When the spa is powered up, the heating system will automatically activate. Whenever the water temperature drops more than one degree
below the set temperature, the heating system will automatically activate and continue to operate until the spa has regained the temperature
loss.