Has anyone attempted a ZCI trailer wire harness install?
Thread Starter
Junior Member
Joined: Jun 2020
Posts: 33
Likes: 9
From: Fairfax County, VA
2008 R320, 2002 E320
Has anyone attempted a ZCI trailer wire harness install?
I am in the process of adding a trailer hitch and wiring to the car. I would prefer not to go through the hassle of changing out a SAM and setting this up with all of the OEM parts, but also read that just tapping into the wires might cause a variety of problems. So I have purchased a Tekonsha ZCI trailer harness, which reads current flow through the wires inductively, and is essentially a reversible installation process with no splicing or cutting. eTrailer and others list it as compatible with the vehicle.
Has anyone attempted this on the W251, or any similar platforms? I've nosed around and found the wires that go to the various lights in the back of the vehicle which should be suitable install points, and was planning to use the ground point in the back behind / above the SAM, and the positive power terminal feeding the rear fuse box. The unit apparently needs an unswitched 12V supply, so I don't need to go find a circuit on an accessory line (unless this kills my battery, in which case I might change it around).
I'll plan to share experiences on this one, but curious if it's been attempted before.
Has anyone attempted this on the W251, or any similar platforms? I've nosed around and found the wires that go to the various lights in the back of the vehicle which should be suitable install points, and was planning to use the ground point in the back behind / above the SAM, and the positive power terminal feeding the rear fuse box. The unit apparently needs an unswitched 12V supply, so I don't need to go find a circuit on an accessory line (unless this kills my battery, in which case I might change it around).
I'll plan to share experiences on this one, but curious if it's been attempted before.
Member
Joined: Oct 2012
Posts: 134
Likes: 8
C63 / E400 Cab
I haven’t seen this before. Looks interesting - i installed my hitch with a factory loom but it doesn’t work.
I believe my Sam has to be changed or reprogrammed. This is probably the same price as getting it programmed or I could put that money towards a DAS/Xentry system.
Please post how you go with it.
I believe my Sam has to be changed or reprogrammed. This is probably the same price as getting it programmed or I could put that money towards a DAS/Xentry system.
Please post how you go with it.
Member
Joined: Aug 2017
Posts: 96
Likes: 13
From: Waterloo, Ontario
2005 E320 CDI,
I just asked the question on the E series sedan thread. I also bought a ZCI kit, and am putting this on my 05 E320 CDI. Was looking for info on the input sensor type on the car.
According to the instructions that came with the kit, ( mine is a Tekonsha 119250) the wiring hookups depend on:
Is it a:
A - 2 wire system,
B - 3 wire system,
BT - brake tail multiplexed system,
BTT - Brake, tail, turn multiplexed system
The hookups for the sensors are different for each of the above.
According to the instructions that came with the kit, ( mine is a Tekonsha 119250) the wiring hookups depend on:
Is it a:
A - 2 wire system,
B - 3 wire system,
BT - brake tail multiplexed system,
BTT - Brake, tail, turn multiplexed system
The hookups for the sensors are different for each of the above.
Thread Starter
Junior Member
Joined: Jun 2020
Posts: 33
Likes: 9
From: Fairfax County, VA
2008 R320, 2002 E320
I should note that 3.5 years in, I STILL haven't tried hooking this up. But since I finally finished building my new Harbor Freight folding trailer, it's definitely time. FWIW I ordered the Tekonsha 119251, which according to eTrailer is exactly the same as their 119250KIT, probably what tbeiler used. I see a video on eTrailer for a GL-class and another for a Metris, so my guess is this can be done.
The connector to the terrible metal plate for all of the rear lights has all kinds of wires and the car has independent bulbs, so I'm guessing that I have independent wires for brake, tail, and turn signals. I don't think the R has dual filament bulbs in the back, but I'm very likely wrong.
This is going down this week so I should have more to report. If I'm the first, that would be awesome, and hopefully can help some other folks thinking of adding towing capability to this beast after it leaves the factory.
The connector to the terrible metal plate for all of the rear lights has all kinds of wires and the car has independent bulbs, so I'm guessing that I have independent wires for brake, tail, and turn signals. I don't think the R has dual filament bulbs in the back, but I'm very likely wrong.
This is going down this week so I should have more to report. If I'm the first, that would be awesome, and hopefully can help some other folks thinking of adding towing capability to this beast after it leaves the factory.
Junior Member
Joined: Nov 2023
Posts: 34
Likes: 11
From: Canadian Maritimes
B250 W246
I'll be watching to see your success. I have been trying to wire up a ZCI to a B-Class with LED lights and it has been a difficult process. I've wired dozens of cars, rewired trailers, even wired motorcycles to pull small trailers, and none of that was as confusing as the ZCI.
