Hi folks,
could anyone tell me the colour of the wires that go to the steering wheel controls on a 1995 P38. I have fitted an aftermarket head unit and I don;t seem to be able to get them to work. Although it could be operator error.
Regards,
Alan

They use a resistive ladder network with the value on a Grey/Orange wire to pin 3 on C226 . The other side of the resistors is grounded via the rotary coupler on the Purple/Black wire.

How do you then interface those wires with the headunit? I have a similar problem

1. Does the DSE have the wiring in the harness for the multi-button wheel I fitted
2. How do I interface with the head unit if it does work?

I remember seeing a PAC-SWI or similar but no idea where it goes
Baffled of Cheshire 😀

DSE, being SE spec, should have the wiring, my ex-plod that was supplied with no buttons and no stereo still has the wiring. Yes, you do need an adapter of some sort. The P38 system uses what's called a resistive ladder network so pressing a button puts a resistance to ground on the wire, a different resistance for each one, 4.7k to ground causes the volume to go up, 15k to ground causes it to go down and a dead short to ground changes the mode. Later systems us a crude data system so the adapter converts the varying resistance from the steering wheel to the data that the aftermarket head unit needs, hence different settings for different makes. The adapter input will connect onto the Grey/Orange wire and ground while the output will go to the head unit.

Hi Gilbertd,
OK, that sounds like I can make it work. I am fitting the same wide screen head that Martin (Marty UK) has fitted and did a write up on this site. It has taken a while but I am getting towards the end now. I will do a write up with photos when I get finished. Thanks Gilbertd.
Regards,
Alan

Thanks for the explanation of the resistive ladder, I had no idea what that meant but makes perfect sense now.
Cheers all