Question about control pannel

My hot tubs pannel that is on top of the hot top will not keep the temperture that we have it set at. It keeps going up. I don't know if I need a new control pannel or if there is another problem. Does anybody have any suggestions. I do not want to spend the money for a new pannel if there is something else wrong with it.

[Mary]

When the temperature goes up does it go to a certain temperature and then stop? What is the actual water temperature? And when you notice this raise, does the spa heater (http://www.hottubworks.com/SpaParts/HeaterComplete.php) come on at all?