A4 B6 3.0 Cabriolet 2003 - Battery Draining - Traced to Radio Circuit

[Forestier]

Hi,
I have been having problems with the car’s battery going flat every few days.
I used the multimeter to measure battery amps and was seeing the reading rise from 20 to 30 milliamps up to 110 milliamps. Sometimes it would rise to 300 milliamps.
Oddly it would return to 20/30 milliamps after 10 - 20 seconds.
It stayed steady for about 30 seconds & would rise again.
Watching the meter, I started pulling fuses every time the meter peaked.
Pulled fuse 39 and meter dropped to 10 milliamps and stayed there.
Repeated a couple of times and confirmed that this was the problem.
Fuse 39 is the radio circuit.
I unplugged the Nav Plus head unit & the CD Changer.
Replaced fuse 39 expecting to see the meter stay at the 10 milliamp reading.
Instead, it showed the same drain as it did when head unit & cd were connected.
So
I assume this indicates a fault in the wiring loom of the radio circuit rather that the head unit & cd.
Has anyone gone down this route before?
Any help much appreciated!
Thanks
PS
I have left fuse 39 out & will measure battery voltage each day to see if it drops significantly with the radio circuit disconnected.

[Crasher]

You are experimenting with a very early CAN BUS system and the way it responds to being powered down and up can be misleading.