Ok, this is not about my 1980 C3, but I am sure it is the same part as in my 78 T/A. Hope somebody can help:

I had (and still have) problems with my high beams glowing dimmly while the low beams were on and ended up checking on the light switch after everything else I did to find the problem didn´t bring any improvement.

I took out the head light switch to see wether it was visually defective which wasn´t the case, so I re-installed it. From this moment on: no more gauge illumination and no more marker lights in the first step of the pull rod switch. The low beams come on in the 2nd step and the interior light comes on when the **** is completely turned to the left.

So, marker lights are the brown wires on pin #3 (or #7, actually I dont recall where I removed the wire) on the switch (to the lower left in my picture, the ones on the copper strip). Upon removal of the switch another time and measuring the switch pins with a multimeter while operating the pull rod in it´s various positions I found out that in "step 1" no connection is made between the +12V (red wire) pin and ANY other pin. In "step 2", connection is made to the #6 pin, right in the middle, bringing the low beams on. Picture attached.









To temporarily "fix" the marker light situation I took the brown wire from the switch connector, tapped into the red permanent +12V in the harness to the switch and installed an old simple pull switch I found in my tool box. It works. Now I have marker lights on the separate switch and low beams on the factory headlight switch in "step 2".

My thoughts were that the headlight switch must have failed due to age so I ordered a new one, just to find out that I still have no marker lights in "step 1". I also don´t have any gauge illumination. The new switch is basically the same than the old one, except there´s a "B" cast in a place on the connector plate while it says "A" on the old switch. There are no pins in this area, though.

I also opened up and disassembled the old switch to understand how it works inside. Two slides make the connections while a cam humb in the rod presses down a pin for interior lights when the **** is turned. I re-assembled the switch and it´s back in the car now. Didn´t help my problem, though.

Can somebody please enlighten (haha) me if I may have dropped a wire while messing under the dash or why I cannot measure any connenction between the pins on the switch in "step 1"?

 

First put the wiring back as it was.

The high beams coming on dim is more likely to be a ground issue, or the dimmer switch being faulty. It cannot be caused by the light switch.
Check and clean the grounds before checking the dimmer switch.

The marker lights are supplied by the tail light fuse, this should be an orange wire at the switch, This wire appears to be missing.