A8 D3 Bluetooth problem

[Bendy]

Good evening,

Hopefully I can get some guidance on a retrofit I've just done on my 2006 A8.

I've removed the existing faulty Motorola 4e086233c fixed phone module and fitted a 4E0 862 335 (HW13) Bluetooth unit I got from an Audi parts specialist. The required wires from the Motorola plug were removed and fitted into the 52 pin plug that came with the Bluetooth unit.

33 Diagnostics - Pin 14.
42 Mic + - Pin 11.
41 Mic gnd - Pin 12.
15 Gnd - Pin 10.
16 Gnd - Pin 2.
35 +12v - Pin 1.

Once this was done I plugged the 52 pin plug in the Bluetooth unit along with the MOST fiber optic plug and the Bluetooth aerial. I then replaced the fuse and switched the ignition on. MMI Screen popped up for a few seconds and then went blank. Checked feed on pins 1 and 2 of Bluetooth unit which showed a healthly 12.7 volts. Removed MOST plug and installed Audi bypass link and everything fired up fine which indicated a problem with the newly fitted Bluetooth module. Refitted MOST plug into unit and switched ignition on, again screen pops up for a few seconds and then blank.

Fired up VCDS and tried opening up module 77 telephone but no connection. Then ran optic test which showed electrical and optical error with 77 - Telephone module.

Am I missing something simple or does it indeed look like the unit purchased from the specialist is defective? When I enquired before purchasing they stated it had been tested and also comes with a 2 week warranty.

MMI is software version 5570 and everything work fine when the Bluetooth unit is bypassed via a MOST link. Bluetooth unit is software version 4E0 910 336F

Thanks in advance for any guidance/help.

Regards

Ben.