headlight switch wiring

[EScanlon]

I'm going to have to dig into the harness in the garage which might take me a bit.

The R/W wire is pretty unique as it only pertains to the High Beam circuit.

The only other extension of that wire in the schematic goes to the Speedometer's High Beam Indicator Lamp.

E

[kenmataya]

i'll have to clip some zip ties to track it, it goes into the wrapped bundle of wires - its 14GA, so i don't think its for the high beam indicator.

[kenmataya]

i'll have to clip some zip ties to track it, it goes into the wrapped bundle of wires - its 14GA, so i don't think its for the high beam indicator.

[kenmataya]

problems solved! the blinker assy is from a different year - only 3 wires ( power from flasher , left, right ) instead of 6 ( power from the flasher, power from the brakes, left front, right front, left rear, right rear ). the front and rears were connected together, power from the flasher connected then they'd run a separate wire to the back to power the brake lights. that line gets pretty warm when connected so i'll add an inline fuse to that for the moment and see if i can fix the mechanical issue on the correct year blinker assy i have. as for the lights issue - the white/red is connected directly to the battery with an in-line fuse - which was blown. thanks again everybody for your help on this one.

[kenmataya]

[Captain Obvious]

Glad you got yours figured out! Now that you've done that, I've got a simple question about my headlight wiring and your thread title is so perfect that starting another thread would be a mistake. (I've been wanting to ask, but didn't want to distract anyone from you...).

I've got a 77 and I want to know why the red/white wire leading to the headlights is a thicker gauge than the other two headlight wires.

[5thhorsemann]

Bruce, I THINK (I say I said I think) it's because the power comes in on the R/W then splits into two circuits (left and right headlight or hi and low beam, I can't remember which) goes thru the fuse box and on to the head lights on the lighter gauge wires.

It's been a while since I got into the wiring on the headlights to do the relay upgrade, but I remember it was a confusing design that seemed to be the product of value engineering as opposed to reliability and simplicity.

[SteveJ]

From the combo switch the red/white wire is split into the left and right headlight circuits. Those wires are the fused wires.

[Captain Obvious]

Thanks for the thoughts guys, but I don't think it's either of those. Let me rephrase with just a little more detail...

Way up by the headlights just behind the radiator mounting plate, there are three wires leading to each headlight:

On the right side, the three wires are a) red/white (red with a white stripe), red/black (red with a black stripe), and c) solid red with no stripe.

On the left side, the three wires are a) red/white (red with a white stripe), red/black (red with a black stripe), and c) red/yellow (red with a yellow stripe).

On both sides, the red/white (red with a white stripe) is a thicker gauge than the other two.

Why? Why? Why?

From the combo switch the red/white wire is split into the left and right headlight circuits. Those wires are the fused wires.

SteveJ, I believe you're thinking of the white/red (white with a red stripe) coming from the fusible link to the combo switch? That one comes out switched out of the combo switch as solid red and goes to the two fuses in the fusebox. Coming out of the fusebox are the hot wires for each side. Right side gets fused solid red while the left side gets fused red/yellow.

I'm not talking about any of that... I'm way up by the headlights talking about the red/white, not white/red.

[Captain Obvious]

Here's a more much simpler way to describe the issue:

There are three wires coming off each headlight. At any instant, two of those three wires have to carry the exact same current... One in, and one out.

What possible reason would there be use a thicker gauge on one and only one of them?

[EScanlon]

The Red/White wire is the RETURN wire for the HIGH beam circuit. The power TO the lamps is the Red (for the Right) and the Red/Yellow(for the Left). BOTH lamps have their return circuit joined at the front of the car for either beam. (Red/Black for the Low).

The original headlights were 45w/55w (if memory serves) which means that the higher wattage circuit (the high) would have required the heavier gauge.

FWIW

E

Edited October 9, 2012 by EScanlon

[Captain Obvious]

Yeah, that makes sense at first blush, but think about it... The same current coming OUT of the high beam on the thicker wire had to be supplied INTO the bulb through the thinner wire.

I'm talking about after they have split for each side. This is right at the connector leading through the fender walls and into the buckets.

I'll snap some pics tomorrow if I get a chance.

It wasn't intended to be an easy question... :classic:

Edited October 9, 2012 by Captain Obvious
Added a little more clarification