Trailer Wiring Finally Installed
After waiting for a detailed post on just how to wire the Bolt for a trailer, I decided to proceed. What follows is how my Bolt was successfully wired. I had this done by a mechanic I trust and the process took over 2 hours. It would probably be much quicker when one knows where to find the wires. Since I didn’t do the actual work, I can only give a description of what I saw.
1. I purchased a Tekonsha ZCI harness
#119250 to avoid splicing into the wiring of the Bolt. The harness wires clamp around each corresponding car wire and pick up the signal of an electric current flow. That means four clamps (right and left turn, brake, taillight) The harness could be removed with no damage to the original Bolt wiring.
2. As many probably already know, the brake and tail light functions in the bumper work only when the tailgate is open. This means we had to access brake and taillight wires somewhere upstream from the tailgate lights, not the bumper lights. Maybe someone can figure how to defeat the GM system that activates the bumper brake and tail lights only with the tailgate open. This would make trailer wiring easier.
3. The right and left turn signals can be activated from the bumper wiring and those are accessible on each side behind the bumper itself.
4. The brake and taillight wiring was accessed by removing the upper rear panel (right or left, don’t need both) in the cargo area. We used the left rear panel. (see photos) Remember the Tekonsha clamps are directional so it matters how they are applied over the wires. The current runs upward toward the roof. Otherwise the attachment process is straight forward.
5. The Tekonsha control unit was attached behind the lower left panel and the trailer wire fed behind the rear panel (which was removed) and then down and out behind the bumper where the trailer hitch had been installed. There was a notch already there from the hitch.
6. The harness needs its own separate and fused 12V line which was fed from the battery (under the hood) and then below the car, coming up in front of the bumper into the same area that the trailer plug exits. Twist ties hold it to the frame but the wire is outside the car. I’m not sure what it would have taken to somehow tunnel it inside the car and still not be visible.
7. The Tekonsha module has a “learn” function, so if it doesn’t work at first it may need to be “taught”.
Feeding some of the wiring without a lift to get under the Bolt could be a real pain.
So far the unit works perfectly. I hope it was built to last since accessing the wiring is not the simplest. Hope this helps others who are planning on installing trailer wiring.