Steering Wheel Circuit Customisation

[JefferiesFarnol]

Hello chaps,
I've installed a new head unit from Continental which I really like, though I've struggled to get the steering controls to work. I bought one of the Connects2 interfaces but it doesn't support the Continental system.

I thought I might try to swap over the resistors on the switch board to the values they need to be for the radio so I've bought a spare switch to have a look.





I've no experience with circuit boards but I think it works like this:

Volume down: no resistor
Volume up: 391 ohm
Track up: 391 + 471ohm
Track down: 391 + 471 + 821ohm
Mode: 391 + 471 + 821 +1520ohm

This seems to correlate with the resistances for the switches that I've read on here.

Someone happily shared the approximate resistances the Continental radio uses which are these:


Volume Down: 0-10ohm
Volume Up: 110ohm
Track Up: 310ohm
Track Down: 460ohm
Mode: 165ohm

If I'm right and the mode button is a combination of all resistors, it looks like I'll struggle to get it to work just by swapping them as the mode value for the radio is not the highest value, though it looks like I may be able to get the others going. Another option I suppose would be to get a custom circuit board made. Am I right or am I over-thinking this? If there's an easier way to get this working I'd gladly hear it!

[JefferiesFarnol]

I've just had a thought, if I cut the connection from the mode switch to the resistor ladder, which I don't think would affect the other buttons, and just soldered in a single resistor of the appropriate value between it and the output wire, surely that would work?

[hogweed]

Don't know about the head unit you're using, but any time I did this you could teach them the values to expect when different wheel controls were switched...?


So there was a menu in the stereo, allowing you to register each button with the device, presumably regardless of the resistance involved


Maybe yours doesn't work that way

[JefferiesFarnol]

Originally Posted by hogweed

Don't know about the head unit you're using, but any time I did this you could teach them the values to expect when different wheel controls were switched...?


So there was a menu in the stereo, allowing you to register each button with the device, presumably regardless of the resistance involved


Maybe yours doesn't work that way

Thanks, no unfortunately mine doesn't have that feature! It's a Continental CDD7418UB-OR and I bought it because it looks OEM as I don't like the usual flashy head units. It's a good unit in most respects but the steering controls are just arbitrary values and Continental have made nothing to use with them. I tested a variable resistor myself and it is pretty much as written in my first post so I'm going to try modifying the switch board which will hopefully work!

[JefferiesFarnol]

Just for anyone interested, I did successfully modify the steering wheel control PCB. I found out the resistance range for each action and bought a pack of assorted surface mounted resistors. Of course, it is a ladder system and there were two slight snags, namely: the first button on the Rover head units has no resistance and therefore no resistor and so I had to break the path, scratch back to the copper and solder a resistor across it, which was not too difficult. Secondly, the 'mode' value on the original board was the final and largest resistance value (all resistors added up) but the value needed for my head unit was not the largest. I solved that by breaking the connection from that switch to the ladder and soldered in a standard resistor between it and the output wire. This worked well and all the others were just a matter of working out the numbers. I tested each combination on the steering wheel control wires that come out of the back of the head unit first just to be sure and I am very pleased to have been successful.


Since most new head units have a programming system for the steering wheel controls, this may not be useful to anyone else unless they, like me, are quite particular about the radio. My next job may be to change the LEDs in the head unit as it is a light amber colour and doesn't quite match the dark, reddish-amber of the 75 interior but I think I'll just enjoy this set-up for a bit!

[hogweed]

Hey, well done you


That's the sort of thing I'd have tackled, back in the day, rather than let it beat me - but I got tired of the fight in the end.


The head units I used generally had a menu function to change the colour, but I imagine you'd have thought of that already if it were the case with yours

[JefferiesFarnol]

Originally Posted by hogweed

Hey, well done you


That's the sort of thing I'd have tackled, back in the day, rather than let it beat me - but I got tired of the fight in the end.


The head units I used generally had a menu function to change the colour, but I imagine you'd have thought of that already if it were the case with yours

Thank you, the quest for The Ideal takes its toll eventually! Alas, no, there is no colour customisation. It's not too far off so I'll live with it for now. Maybe when I run out of other finicky tasks I will investigate the prospect of modification.