Audi Trailer wiring

[George Harris]

I have just finished building my 4' x 8' utility trailer, and welding up
my own hitch, and ran into a little snag when doing the wiring.

The car is an '87 5kcstq.

Wiring system is six pole:
1) one wire to ground at the grounding point by the rear left light module.
2) running light, taken from left rear module.
3) brake lights taken from left rear module driving both trailer brake
lights.
4) left turn indicator taken from left rear module.
5) right turn indicator taken from right rear module.
6) Not using the sixth wire.

Problem is when I put on the brakes, the proper bulbs light up, but the
brake warning light comes on. Is the system detecting an imbalance
between left and right? Do I have to wire the left trailer brake light
to the left car brake light, and the right trailer brake light to the
right car brake light?

I've always found trailer lighting challenging :-)

Cheers
George