Unidentified relay
 

There is a strange relay of some kind attached to the right side of the Air Conditioner Vent box on my 68 C20. I can't find anything in any wiring diagrams what it is. While its connected to the A/C vent box, I am not sure it is related to the AC. Can anyone tell me what this is and what the different wires are supposed to be connected to? Note..the image is upside down..not sure how to fix that. THe locatin of this is under the glove box on the right side of the truck.

Re: Unidentified relay
 

Probably looking at the wrong schematic. The general schematics do not show the A/C system, it is a seperate dedicated schematic.
Take a look in the 68 factory chassis service manual section 1A-34 and -32. Looks to be the A/C blower relay. From what I see the wire colors match perfectly. RTFM

Re: Unidentified relay
 

Anti dieseling relay used for the heat/cool fan high-speed.
Working on mine in my 68 today!
Mike.:chevy:

Re: Unidentified relay
 

Indeed after some late night study I found that reference. I am giving some thought to rewiring the truck as the fuse box is badly corroded and has had to be bypassed a couple times. There's been so much wiring bypasses done (incorrectly) over it's life that I'm not sure just replacing the fuse box is enough, even if I could find one.

SO trying to identify all the wires, both stock and aftermarket.

Re: Unidentified relay
 

Blower relay for A/C. Not the anti-dieseling relay - that is attached to the dash.

Re: Unidentified relay
 

When I got my truck many years ago it had a broken control module for the heating/ac system. This was back before GM started making replacements again. Since the AC switch was tied to this broken module, some rewiring was done. A toggle switch was added and the AC power was routed through it. The thing is, there was a wire tapped off the AC fuse to this switch, which then runs direct to the AC.
Also, it looks like the purple wire is supposed to go to the unfused port on the fuse box but I see an orange wire there instead. I have not tried to trace any other wires.
What exactly do the resistor and relay do?