Originally Posted by Hvacman
The cup holder that has the selector switches is connected to an electronic module that control all functions. Only the heat doesn't work. Dealer says its obsolete for a 2015 model. It is a 3970 and not a 3770.
'The dealer says', so much help there. As Arron suggested, get out the VOM and start checking voltages to and from the switch location.
If just the heater is out then a normal continuity check on the element is in order.
Obsolete, maybe the dealer is obsolete but electronic components and circuit boards aren't proprietary to RV dealers. Only a few manufacturers make their own stuff.