How to Install the ZCI Wiring Harness Part # 119250KIT on a 2-Wire System


My buddy and I tried our best to get this to work on my car but to no avail. I easily found the left turn signal wire but on the right hand side all the wires read the same volts even with the right blinker on. Therein, I have no idea what is brake, running lights etc. The wiring kit I bought from you was the recommended one by one of your customer service folks. Tekonsha 119250-037 trailer light wiring kit


Expert Reply:

It sounds to me like you have a 2-wire system on your 2015 Mercedes-Benz GLK. For vehicles that use a 2-wire system, the turn & brake functions are combined on one wire and the tail light function is on a separate wire.

The easiest way to test the rear taillight connectors for the proper turn/brake and running lights signals is to use a circuit tester like part # 40376. A voltage meter is not necessary to install the ZCI Circuit Protected Vehicle Wiring Harness part # 119250KIT. In order to determine which wire represents which function you will need to have a friend sit in the vehicle and perform each function while you are testing the wires.

Once you have determined the correct wires at the back of the taillight housing, you will want to attach the connectors from the kit to the corresponding wires. For a 2-wire system, the connector with the yellow tape will need to be attached to the left turn signal wire. The connector with the green tape will need to be attached to the right turn signal wire and the connector with the brown tape will need to be connected to the running light wire. The red wire will not be used for a 2-wire system.

You will also need to wire both the ground and power circuits coming from the converter box. The ground wire will need to be attached to a clean, bare metal surface on the vehicle's frame and the power wire will need to be ran to the battery's positive terminal with a 15 amp fuse placed 6" before the battery.

I have attached a installation video on a similar vehicle for you as well.

expert reply by:
Conner L

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