If it's the basic, under-dash heater assembly, you need FAN and DEFROST.
The Defrost lever runs a cable pull to a door in the heater duct--the door diverts air to either the under-dash vent, or up to the defrost ducts.
If you make your own wiring harness, get a copy of the factory shop manual so you can see how things connect.
I just replaced my heater switch with a brand new one, and replaced the heater motor with one taken from a junk yard truck. The switch only ran on High, and either the switch or the motor were had too much resistence and started to burn the wire and popped fuses.
To replace the rivets on the back (mine were broken too):
I removed the frame for the switches from the bezel.
Center-punched the old "rivets." These are really swedged "pins", like how they connected the body to a chassis on a Hot Wheels car.
With a very small drill in my drill press, I drilled into the old rivet area. MARK YOUR DRILL BIT! Put a piece of tape on it to act as a stop. If you go too far, you'll punch through the face of the bezel.
I then took very small pop rivets and resecured the switch mount to the back of the bezel.
Good as new. I now have three fan speeds, no more blown fuses...and a heater that is still very undersized for a Suburban!
Brad
