Thanks A1EK, your detailed response has provided the missing link.
I’m going to add the reference terminology from the user manual (page 88) Multifunction Steering Wheel Display (as a reference for future users – link below)
http://www.mbusa.com/vcm/MB/DigitalAssets/pdfmb/ownersmanual/2000_clk_cabriolet.pdf
The biggest problem was getting the Multifunction Steering Wheel Display to show “Blank” (as it was constantly coming up as the default "Odometer" mode, or as “Audio ----“ , in the example picture for the web below its showing the "Trip Computer" mode).
I still don’t know how I got the display to show “Blank”, I must have tried it 50 times and got there about 5 times (to allow the unit to be programmed up).
The sequence of events on how I got there is still beyond me.
Hopefully yourself or someone else can remember how to do this.
I have an technical background and am comfortable with most electronics so this has been fairly frustrating exercise.
I got the following items working earlier in the day, but went out in the car just before, and I can’t get it to work (Multifunction Steering Wheel Display back to showing “Audio ----“)
Will have to try again later.
I was going to tell you that I managed to get 4 out of the 6 functions you suggested to work OK.
Increase Volume - Got this working as Increase Volume
Decrease Volume - Got this working as Decrease Volume
Next display - Got this working as Radio Pre-set Up
Previous display - Got this working as Radio Pre-set Down
Next System - Couldn't get this to work (because as you press it, it changes the function of the display)
Previous System - Couldn't get this to work (because as you press it, it changes the function of the display)
Dial Telephone Number - Couldn't get this to work (because as you press it, it changes the function of the display)
End Telephone Call - Couldn't get this to work (because as you press it, it changes the function of the display)
I programmed up the Volume + & -, then skipped mute (press program on the SWI-RC) , then Next & Previous System, then left the SWI-RC to time out so that the programming function would end
So I did get 4 out of 8 buttons working (for about an hour, before it went back to " Audio ---- " mode.
The switches for the units were set as follows :-
SWI-CAN2 switch to 4
SWI-RC switch to 7
BTW, when I mentioned the LED was ON, this was for the SWI-CAN2 (there is an LED inside it that is hidden (aka no peep hole) but I’m not sure what it indicates, I assume it comes on when the CAN BUS cabling is OK, as it went off if I reversed the wiring).
You are supposed to see the LED in the SWI-RC (as it has a peep hole) that you use to verify version number and programming information.