Horn Repair Outline, Clock Spring Ribbon Cable: 2013 TRD OffRoad

Here I outline the repair of my 2013 TRD Offroad Tacoma's clock spring ribbon cable (“device”), which was preventing the horn from working. I'm not a regular user of my horn, so I can't say how long it had been since it worked. My truck is also low mileage for its age ~50K miles. I noticed my horn didn't work a few months ago, when someone squirted across a highway too close for my comfort. I can't say if it worked at different positions or not. The other steering wheel functions (cruise, airbag, audio controls) all worked and continue, to the best of my knowledge, to work.

There are several guides for disassembling the steering column. I will add a couple tips for that process. Have your wheels pointed straight or locked out to either side when disassembling to allow for ease in positioning the “device” in its’ range of motion. Lastly, making matching marks on the steering wheel and steering stem allows for easily reinstalling your steering wheel in the original orientation.

Contrary to the picture above, I would remove the device from the steering column before separating it. The catches in both cases are straight-forward and self-evident. To remove the airbag leads from the airbags you must pry out a colored center clip before pulling the leads from the airbag/horn switch. Which leaves you with the leads still attached to the device as shown.
When separating pay attention to the cable routing, as shown, though the device is asymmetric which allows for ease of reassembly.

I didn't notice the break in the ribbon cable at first. I suspected the connectors or the folds in the cable. It turns out I did not need to take the device apart any further than above to repair. However, I'll continue in case it’s helpful to anyone. The end shown below was the tricky one to remove from the larger device. As pictured below, on the outside, deep inside, is a catch which must be depressed. I had luck from the wire lead side. Along with two catches on the bottom which are obvious and one catch which goes over the top of the main device body.

If, like me, just one steering wheel function is affected you can locate which trace carries that function. For the horn, on a '13 at least, the dash side connector with a green-red trace wire carries power from the relay activation coil through the ribbon cable to the airbag/horn frame via a blue wire. Which, when the airbag/horn section is depressed, grounds the relay coil, activating the relay, sending voltage to the horns themselves as shown in the following wiring diagram.



Above is offending break seen as a small black spot in the trace. Below is a picture of that break, under 80X magnification. I suspect my manipulation of the ribbon, in searching for the problem, might have caused the break to become more distinct.

To repair, quickly touch a pre-tinned soldering iron to the break. The iron easily melts through the protective coating. Minimize excessive melting and especially straying from the broken trace. After repairing, check with a multimeter that the trace has continuity between each contact. I then filed the solder as flat as I could without damaging the cable further, with below as the result.

To finish I covered the trace with 5 min two-part epoxy as smoothly as I could. The clock spring device has a little over 5 complete revolutions for range of motion. If your wheels are pointing straight when you disassembled, then reinstall the device in the middle of its' motion, or 2.5 rotations from either stop.

 

Did you measure the width of the ribbon? I am wanting to add a ribbon to install a heating element for my steering wheel. Cheers