antichristpm

For my next trick (for carputer project) I'm going to try and hack the mute button. Does anyone know where the wiring leads to for the steering wheel controls?

Sin,
-Paul

B-Nez

Here's a schematic for the switches, plus the pinout for the audio unit connector:

antichristpm

Awesome! Thank you!

antichristpm

I have discovered via the diagram, and visual inspection this weekend, that the steering wheel controls are multiplexed onto a single pair of wires to the stereo. My question is now does anyone know where the original pairs of steering wheel control wires go to before multiplexed into a module? I searched underneath the steering wheel and am a little hesitant to open the ticking airbag timebomb of my wheel unless I absolutely have to.

Help?

Sin,
-Paul

Sputnik

It's not a box that "mulitplexes" the signals into a single wire, it's much simpler than that. Each audio control button on the steering wheel has a different resistance level. In other words, when one button is pushed, it would be 100 ohms, another would be 200 ohms, another would be 300 ohms, etc. etc. The head unit can determine which button is being pushed by the resistance. Thus, no multiplexer box or other complicated electronics required.

This is something that is used in many many cars with steering wheel mounted controls, whether they be for the radio, cruise, or whatever.

---jps

English

I'm reading a book in which a man is found with a screwdriver through the heart.....yup....trying to steal an airbag and boom...dead. I wonder if that has happened in 'real life' or if it's still just fiction.

antichristpm

Oh I believe the screwdriver story... don't %^*k around with airbags folks.

On another note, if these buttons are all of different resistance where do they lead to before being merged onto this one wire? Inquiring minds need to know.

Sin,
-Paul

Sputnik

Normally, the buttons on the wheel are just one unit, all wired together at that point. If there are two sets (one on each side), there is normally a wire run between them, and then from them into the coil wire. There really isn't any way to separate them without taking the switches apart altogether, re-wiring them, and then adding enough coil wires.

---jps

antichristpm

Well then... I guess to hell with that idea. I'm back to purchasing an aviation quality Push-To-Talk switch.

Sin,
-Paul

Sputnik

Or, you could build a circuit to decode the signal like the car radio does.

---jps

antichristpm

That's true but not what I'm looking for. What I wanted to do is wire (in parallel) my MIC line through the mute switch so that when I depress the mute switch it mutes the volume on the stereo and also makes the MIC active for me to issue voice commands... hence Push-To-Talk.

Sin,
-Paul

bureau13

How much work did you want to put into this? You could conceivably make your own little decoder box to figure out which button is pressed, and have this trigger a PTT relay. I don't know if its worth the effort, but its certainly possible.

jds

antichristpm

Decoder box? Man all I want is a simple push to talk relay... it would have been nice to wire it like I mentioned into the mute switch but instead I'll go for something like this: http://shopping.pilotportal.com/cata...?productid=696

Sin,
-Paul