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Trailer wiring - Tekonsha ZCI 119251

Hi folks,

Been trying to get trailing wiring set up on my 2018 Model S 100D, using the Tekonsha ZCI 119251. These are what I've found for wiring on my car tail lights so far (couldn't find any matching posts with this details, hopefully it may also be useful for someone else):

Driver Side:
White/red - Left signal & brake
Blue/red - Left signal & brake
Gray/red - Left signal, brake and tail light
White - High when lights off, intermittent on left signal, high when tail on, off when brake on
Black - Ground

Passenger Side:
Yellow: Right signal & brake
Black/red - High when lights off, intermittent on left signal, high when tail on, off when brake on
Brown/white - Right signal, brake and tail light
Purple/black - Right signal & brake
Black - Ground

I've tried multiple configs from the Tekonsha instructions - trying to get the "A - 2 wire system" working using white/red on left and yellow on right, plus brown/right on right for tail, and brake not used. Also tried BTT, with left signal on gray/red and right signal on brown/white, with tail & brake disconnected. So far, not a lot of luck. It seems I can get tail lights and brake lights working, but no luck getting anything from the signals in either config.

Curious if folks have any ideas or see any issues. Thanks!
Some other quick clarifications:
- I've been pulling the fuse and doing the re-training each time I change configs
- In the former config (white/red on left and yellow on right, plus brown/right on right for tail): left signal - nothing, right signal - tail lights intermittent, tail lights - correct, brake - correct, tail lights + left - correct, tail lights + right - just taillinghts
- In the latter config (left signal on gray/red and right signal on brown/white), results are: left signal - nothing, right signal - nothing, tail lights - correct, brake - nothing, tail lights + left - correct, tail lights + right - correct
I just installed the same light adapter last night on my '15 85D (left/right/tail wires used, left the brake one un-used). I was unable to get the trailer to work unless the lights are set to parking or auto. When the lights were off, the left turn signal and brakes worked fine but with the right turn signal on the left lights and running lights would flash on and off in sync with the right signal lights (see video). When I set the lights to auto or on, everything works as expected. I always leave the lights on automatic and check the trailer before driving so unless you or someone else knows why it's happening I'm not going to put anymore time into it.

Just following up on this @dmwahl @jeffwick to ask what your perspective is now that you've gotten it wired up. I picked up a light-weight fiberglass camper (see pic -- it's only 1100lbs dry), and while our other vehicle can tow it I'd love to also be able to tow it with my 2016 MS. My eco-hitch works great (I towed it around our sleepy street), but it's not road legal (obviously) without lights, and I'd also like to make use of its brakes as well for safety.

I'm not one of those folks who is confident/experienced enough to do the wiring myself, so I'm struggling to figure out how to find someone who can do it for me; and I also worry about voiding the warranty.

Thanks for any guidance you can offer.


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@ropero , I never did get that product to work. I ended up instead going with the Tekonsha 119148 ModuLite HD Protector Trailer Light Power Module Kit. It works pretty well, other than tail lights - there wasn't a dedicated wire at the rear lights for that. I probably could hook up to the license plate lights, but that wasn't easily accessible.
@ropero I think Uhaul will install them, but I'm not sure. Call around and ask, it's not particularly difficult if you're used to doing it. Regarding towing with it, I basically just have to remember to turn the lights on manually (vs automatic mode) when towing or they don't work properly. I don't really feel like that's a problem, you should always check your lights and know what you're doing anyway. At 1100lb I personally wouldn't worry about using the trailer brakes, if anything I'd want the car to do the braking so I can capture the energy with regen.

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