The Stovebolt Site Forums The Shop Area The Electrical Bay Headlight switch "schematic"

Can anyone lead me to a diagram of what terminal does what on a headlight switch for a 65? (I think 64-72 were the same?). I want to understand this switch so I can see if my old one is really dead, or if I am just wasting my money on a new one.

I could also use some guidance on different testing procedures for the switch. I did see a decent post by cjoe on 2-16-2007 that gave some advice, but It would be helpful to know what terminal is doing what.

If there is no resource known, maybe I will post my own testing results, although my electrical skills/understanding is definitely "apprentice"!

can anyone recommend a good book or website that guides newbies through automobile electrical testing and troubleshooting?


Thanks, Jerry.

Jerry,

Take a look at this. It's a '66 switch but maybe it will help.


http://home.earthlink.net/~hilandr451/_uimages/HEADLIGHTSWITCH.jpg

Stuart

Stuart,

Thanks so much for this! It is a great diagram. I am struggling with understanding the electrical system and this helps. I was just out taking notes on the connectors, the color wires attached at the harness and double-checking with the '65 supplement wiring diagrams. Your post confirms my notes.

I still was not able to make any conclusions with the ohm meter on the contacts of the switch. From battery (red) to the headlight terminal (lt. blue) I got a reading, and on one other, too (can't remember which). But all others gave no movement of needle... not the dome light, not even the instrument panel, where I expected to see a varying resistance.

I plugged in the new switch and all the lights are working properly now... so problem is fixed, but I haven't learned much.

Jerry

The thing that is confusing about the light circuit is the tail & dash lights are on a different circuit from the head lights. There is a separate hot wire that comes off thefuse panel for these. They do not get the curent from the same hot wire that feeds the headlights. The dome light is grounded through the light switch.

Here is a link that helped me figure out the light switch when I had a problem with my lights headlight switch

oldgmc,

I'm jealous..your picture is much better (more clear) than my picture.

Stuart

Wow, where do you guys find these awesome photos and schematics... not from the manual, I know that!

Thanks for all the help,

Jerry

Just an update, after I swapped my headlight switch with a new one, all worked fine. Then a week later (yesterday) I went out for a ride and the brake lights, turn signals, dome light (and possibly the dash lights--hard to tell in the daylight) were all NOT working! I looked at the fuse and it seemed to be okay (hard to tell down in those shadows). I tried to pry it out with a screw driver but it wouldn't move... so I walked to the garage for my VOM meter and on the walk back to the truck the brake lights were working (I had a stick wedged between the seat and pedal). All was working now! Maybe I've just had a bad connection at the fuse all along? I am going to put the old switch back in just to see. At $26 for a switch, that's an expensive mis-diagnosis!

6066gmcguy has great info on testing for lighting troubles:
http://www.6066gmcguy.org/headlight.htm and
http://www.6066gmcguy.org/Electrical-01.htm

The are some testing basics that I think I need to learn before I can really use his info... He describes testing for 12 volts at the headlight switch with the switch on and getting12 v. at a certain post on the switch. How do we phyisically get the probes in there? Is this where I would use a pin stuck through the wire's insulation?