That might have helped, I didn't think of applying beer. I did have a couple, then walked away to think on it. I came back several times to re-check what I had done. It was tricky because the harness didn't have the same color wires as the schematic, then the schematic that I found on line had to be reversed to match the layout on the car. I didn't have to stress too much because I'm just test fitting my parts before paint, but it was causing some delay. Actually the most that I did get done was on a late night with a few beers, but 12 would not have been good. Thanks again

 

With the ignition on and the head lite switch off, the light blue wires going to relays 2 and 3 are providing the ground to the relay coils through the dimmer switch and head lite element. With the head lite switch on, the head lite is consuming the voltage at the head lite and the light blue wire to relays is now a positive potential, the same as the brown wire, de-energizing relays 2 and 3. The drawings I've have show this.

 

Thanks, that does help to explain the system, it seems like there must have been a simpler way to achieve it though. I'll hold on that diagram, I may need to share it with the next guy.

 

What book did you copy that from, it seems like it would be a good one to have ???

 

I'm not sure of the proper name. I think it is called 67 RS Console and Headlight wiring manual. Here's a link to several ebay auctions. Without some background in electrical controls, this system could be a nightmare for a owner. Pretty sure that is why it ended up a one year only design.

 

From what I hear, the vacuum controlled headlights weren't one of Chevrolet's greatest achievements either, seems to be why so many are converting to electric

 

I guess that's why those guys make the big bucks, to prove that they create something to outsmart the rest of us. I've looked over the diagram, and I can follow it now. I was having trouble understanding the residual voltage that I was getting , and what it meant, I didn't know that it was just from the relays looking for a ground. I had no idea that it would get its ground through the bulb. ????? Thanks again, it may be of help later understanding the system if I ever need to troubleshoot a problem. Ernie

 

I don't know if I would call this residual voltage. Current is going to find the shortest path to ground. When the switch is turned on, 12V is now being applied directly from the switch to the light blue wire at the head lite and that is now the shortest path to ground through the element. This action also directly applies 12V to the light blue wires to relays 2 & 3 coils, making them the same potential as the opposite side of the coils. In effect, this de-energizes the coils because they no longer have negative potential available.


It just dawn on me what you were calling residual voltage. The voltage between the light blue wire and a ground when there was no lamp in the system. Yes, you're right, any connection between these two points with a meter or test light would show a voltage because both devices would be completing a ground path through the device. At first, I thought you were referring to having 12V on the light blue wire when the head lite switch was on.

 

Yes, I guess that I was using the wrong term for what I was seeing. The voltage that I was seeing with a test light looked more like 4 or 5 volts. I didn't know what to make of that, but it does make more sense now. I wasn't imagining the system finding ground through the bulb, does that mean that if the bulb is burned out that the doors won't close ???

 

Not as long as one was working. The lamps are wired in parallel, so if one lamps element burnt out, the other should still provide a path to ground.

What you were most likely seeing was a voltage drop from going through the relay coils. The coil of a relay has a continuous wire wrapped around a steel core. When energized, this produces a magnetic field around the core that opens or closes the contacts of the relay. Because the coils have not been energized, the wire of the coil becomes a conductor in the circuit and creates a voltage drop across the coil by adding the length from the coil windings to the circuit. Think of it as an extension cord, the longer the length of the circuit, the less voltage available at the farthest point.