passenger side temp control
 

1998 Deville D'Elegance
Hi Guys, I am having a problem with the Passenger side personal temperature control. When I turned on the air for the first time this season I note that only heat comes out of the "passenger side" vents yet cold air comes out of all other vents.

This of course tells me the passenger side temp control system is screwed up but I haven't a clue how it works so its difficult to know where to start looking for a problem. There is two voltages at the rotary temp control knob which is located in the passenger door arm rest, 12volts and 5volts. Can one of you guys give me a brief description of how this thing works???? ie: is the switch simply controlling a flapper somewhere that blends the air/heat for the two "passenger side" vents?? Is the rotary temp switch outputting to a circ board or would it output directly to a damper?

Any help or suggestions greatly appreciated.