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Product Review: Tekonsha Modulite ZCI


Tekonsha ZCI System

We “lost” our TOAD (the Jeep we tow) signal lights shortly after we had our engine overhaul in Superior, WI.

So for several days we were driving around illegally. Bad mojo.

We tried to get it fixed at a Cummins/Spartan shop in Fargo, but after 3 hours the techs couldn’t locate the problem, and we weren’t about to give them carte blanche at $118 per hour.

Now what?

I didn’t want to try fixing something professionals couldn’t remedy. But what about installing another TOAD lighting system?

After searching online RV forums and lots of Googling, I thought I found a solution — Tekonsha ZCI System for about $124.

Tekonsha ZCI & 4-Flat to 7-Way Adapter

I looked at a Hopkins system, but to use it I would have to “cut” into the RV’s wiring.

The Tekonsha system is described as a Zero Contact Interface (ZCI) which means there is no cutting. The Tekonsha system uses induction — each light sensor wraps around a wire (for example the brake wire). When the wire is energized, the Tekonsha system converts it to a voltage.

It sounded too good and too easy to be true, but we were desperate. We needed a TOAD lighting fix right away, and I loved the idea of not cutting into our RV’s wiring.

Here’s my Tekonsha installation story . . .


There are several types of vehicle wiring that the Tekonsha ZCI can handle:

  • 2-wire system: The vehicle’s turn & brake functions are combined on one wire and the tail light function is on a separate wire
  • 3-wire system: The vehicle’s turn, brake and tail light function are on separate wires.
  • Brake/Tail multiplexed wiring system: The vehicle’s brake & tail functions are combined on one wire and the turn functions are on separate wires
  • Brake/Tail/Turn multiplexed wiring system: The vehicle’s brake, tail & turn functions are combined on one wire

Our Newmar uses a 3-wire system. To determine what wire did what I had Jan use each turn signal, the brakes, and the headlights. I watched which tail light bulbs came on and mapped each one’s function:

Light Map

After finding out each the function of each tail light, I identified the wire that powered each bulb. To do this, I exposed part of each wire and then connected the wire to a multimeter.

Wire Testing

So far so good. I was able to identify the wires for the left and right turn signals, the brakes, and headlights (taillights).


The Tekonsha system must be connected to a permanent 12V power source — that is, directly to the RV’s engine battery.

Tekonsha System Power Wire

The hardest part about this was routing the power wire from our RV’s pullout battery compartment up into the back of the RV.

The power wire uses a 15A fuse which alse serves as an installation “switch”. When you first activate the Tekonsha system by inserting the 15A fuse, the system must be “taught” or sync’d. To do this you just flash the left turn signal 5 seconds, the right turn signal 5 seconds, and so on. Not a big deal. However, if the Tekonsha system is disconnected from its power source, you’ll have to re-sync the system.


Truly, the easiest part of the install. You just need about a 3-inch length of wire for each sensor to clip onto.





The Tekonsha system comes with a 4-flat output. Because our Jeep is set up for a 7-way interconnect, I purchased a Hopkins Trailer Wiring Adapter that converts a the Tekonsha’s 4 flat output to a 7-way output:

Hopkins 4-Flat to 7-Way Adapter






4 Comments Post a comment
  1. Tim #

    Way to solve this problem Tom!

    August 16, 2017
  2. #

    Damn good problem solving, Tom. Can’t help thinking though that you don’t need any more problems. Kath

    August 16, 2017
  3. Tom! You r good at finding the problem & then carrying out the fix. Ok , let’s all think positive now. Njhz

    August 16, 2017
  4. emhuze609 #

    Wow.. after all that hard work, effort, research, etc. One really wanted things to work out.. and it did.. Great Job Tom!!


    August 16, 2017

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