I’m working on a project to add turn signals in the side mirrors of my ‘84 TA. I plan to use a side marker light socket for the light inside the mirror. This light socket has two wires. I want the light inside the mirror to be on with the parking lights and blink when I use the turn signal. Referencing the factory manual below, the side marker has two wires: lt blue or dark blue (depending on side) and brown. Does the brown wire act as a ground or a second positive input? Trying to figure out how the front side marker is grounded?? Seems like just the front park / turn lights above the bumper have a third ground wire. For the light socket inside the mirrors would I connect one wire to blue and the other wire to brown? Or should the brown and blue wire connect to the positive of the light socket and then connect ground to the other?

 

Based on that wiring diagram, it looks like it's using the filament of the indicator as it's path to ground. When the signals are off, it would be at 0v, so it would have difference present. When the turn signals are illuminated, the voltage becomes the same on both sides, meaning there is no difference and the bulb is off, which would provide a flashing effect.

 

Ratfink is correct about how the circuit works.
The mirror bulbs will have the same connection as the front side marker lights.

Left: Lt. Blue / Brown
Right: Dk. Blue / Brown

You can tap all those wires under the dash by the steering column / headlight switch.

 

Thanks so much guys!!
I tapped into the lt blue / dark blue and brown wires under the dash and ran new blue and brown wires to each door. I’m still waiting for my mirrors to get painted but I connected a light socket to the new wires for testing and they work perfect: the light stays on with the parking lights and then blinks when using the turn signal. Super excited!

 

Nice! Post pics when it's finished

 

Project not finished yet but getting there. Side mirrors have finally been painted. I wasn't sure if the turn signal mod would actually turn out but they look awesome! Can't wait to get these mounted and functional.
You can see more info on how these were fabricated in my build thread HERE

 

Mirrors installed and wired. They come on with the parking lights and blink with the turn signals / emergency flashers. Turned out pretty nice.

 

Oh, that's super clean. I might have to steal that when I take everything apart to do the heated mirrors in mine.