I got a new rear harness for my 1979 flareside. The harness is made for styleside I think. There are 3 plugs coming off the harness in the rear. One for brake/turn, one for reverse and one for marker lights. I'm using the marker light wire for my license plate lights.
The brake/turn plug has 3 wires, one for marker, one for turn, and one ground.
The reverse plug has 2 wires, reverse and ground.
The taillights for the flareside are trailer style lights w/ 2 bulbs. The bottom bulb has 2 intensities, low and high. The light itself has 3 wires.
I thought one of the wires was a ground and the other two seem to energize the respective bulbs.
How do I wire up my harness to this 3 wire light? Do I not use the marker wire in the brake/turn plug and just wire the turn/brake wire to the bottom bulb and the reverse wire to the upper bulb?
Oh and the harness is spliced into the correct wires from the original loom (yellow for left turn, green for R turn, black w/ red strip for reverse, brown for markers). I added the additional wire for the fuel sender as well into the new loom.

Black=ground, yellow=turn, brown=marker

Light green=reverse, black=ground

black=ground, yellow=turn, red=reverse

 

I might have found the answer to my question. It looks like a 3 wire light is not meant to have reverse. I would need a 5 wire light to have reverse.

 

There are no three wire light bulbs as there are simply no bulbs offered. You have a two element bulb, it has a ground, it has two contacts, you'll see one element is thinner, it burns with low intensity and it is used for tail lights (along with tag lights and marker lights) ... the other one is fatter, uses more watts to light, is higher intensity, it is used for turn and brake light.

A BU light will use a separate socket. It is a single element bulb.

Each bulb gets a ground.

Maybe I missed the question? ​​​​​​​

 

I figured it out. I was under the assumption that the tail light supported a BU light, when in fact it doesn’t.

 

I thought you were awfully close to it, sometimes it just takes a tick and one suddenly sees they had it.