Frede (No City)
In some applications, an auxiliary switch was used for driver and co-pilot 12-volt fans. For other tasks it may operate a lamp or an electric step. More detective work is needed. I'd suggest gaining access to the rear of the switch and see how many poles and how many wires are attached, if any. A positive 12-volts on one of the wires is another good clue that it indeed operates some thing. See if you can find out how many wires, how many poles, is the switch "hot," and if it's a momentary switch or one that remains in both the on and off position? The more clues, the better. But if no wires are present, it's there simply to plug a hole in the dash!