Tex: The original heater switch is a brown plastic switch that has three positions on a flat brown plastic toggle that goes up and down. The maroon replacement switches with a rheostat type of setup are not original and are not what came on the truck from the factory.
Here's a photo of similar switch. The difference in the original is that it is brown toggle with "heat" on it instead a white toggle with "air" on it.
[img]
http://www.oldgmctrucks.com/photos/stovebolt/heaterswitch.jpg[/img]
It mounts under the dash between the defroster cable knob and the column.
