Here is some info on another A4/B6 forum I posted some time ago..........
Both the coin holder and cup holder illumination works in the same way. At the back of the respective items there is a small plastic rectangular clip-on box containing 2x red LED's with a 2pin (0.1" pitch) electrical connector. Connecting 12v to this gives the illumination to the LED module. This red LED light is then transferred to the front of the unit by means of a fibre-optic conductor - it's a strip of thin perspex. At the front of the unit, i.e. where the white icon is, there is another fibre-optic conductor that picks up the light and carries the light through 90degrees to the back of the icon - they must have spent millions developing this!
Is your unit compatible for illumination?
Check to see if there is the LED module on the back of the respective unit - if YES - wire it up and have a beer!
If not, then I'm afraid it's off to the stealers or fleabay
Can't I add the LED module?
The LED module does actually detach, but it has no part number. I have scanned the Official Audi parts database (EKTA7) and there is no mention of it specifically for these items - you would also require the fibre-optic conductor.
Now I did take an LED module and a fibre-optic strip from a fleabay donar coin holder and managed to install it into my lightless unit - HOWEVER, the front icon was very dim on my original tray unit - it transpires that my lightless unit did not have the icon illumination fibreoptic strip directly behind it - just air. This was again confirmed by removing the donar coin tray and installing into my own housing. It now illuminates brilliantly.
On the part list "cup holder" page, there is an item named "fibre-optic conductor", part no. 8E0 857 355, priced at £6.15+VAT. My parts guys at Audi knew nothing about these items and where they are used?? If this is the LED module and fibre-optic strip it may work although not 100% since the back of the icon lacks an illumination strip which can't be added to the already glued fronts of the respective units.
If you are looking to buy a donar/replacement unit off fleabay ask the seller the question - "Does the coin/cup-holder have a small led module at the back of the unit with a 2-pin electrical connector?"
Also beware that other Audi models use different coin holders and I beleive cup holders, make sure you buy a specific A4 unit. (These items are also RHD, hence the 8E2 part number prefix.)
Audi part numbers:
Cup holder: 8E2 862 534 J5 PR @ £22.39+VAT (based on 15/08/2008)
Coin Holder: 8E2 941 561 C5 PR @ £26.05+VAT(based on 15/08/2008)
Fleabay "A4 Cup Holders" are rare, let alone illuminated - I did actually give into the dealer "Cup Holder" part and after looking for 3 months on Fleabay - I had a weak moment!
Some dealers will tell you they have never been illuminated....... here are some pictures of mine anyway!
Parrot has now gone as have fitted OEM BT.