cheers for reply GenePoole. Yeah I know I need coding - already arranged with an Autologic equiped dealer in the UK and a CDC is not required - £80. I've been all over the e90 forums over the last few months making sure I've researched before attempting the install myself. Nearly there...
using the CDC power and ground cables has been done by others:
http://www.e90post.com/forums/showthread.php?t=391473
http://www.e90post.com/forums/showthread.php?t=84125 - note comment about using CDC powersupply
I've also installed the Dension AVR in the trunk alongside the GW500. Running the cables from the head unit for this was the hard part, but all done succesfully, and powered up ok (power comes from head unit harness). Thought I was onto the "easy" bit of simply connecting up power to the GW500. once that was done I was going to switch the MOST ring fibres - No point switching them and losing the radio/bluetooth if the GW500 has no power...
I can power the GW500 direct from the battery terminals (and tested this), but would prefer not to so as not to risk a drain on the battery. the CDC cables would be ideal. I can't see coding the enabling of the CDC suddenly turning on the 12V supply to the CDC, but you never know. Other folks that have installed a GW500 succesfully all seem to have powered up the unit, then gone for coding. (The GW500 has to be visible on the MOST ring to allow the coding I think..)
with a multimeter, the ground on the CDC wires traces back to the ground on the battery ok, but the power wire has no 12v with car key out/key in/engine running....