[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!