Just an update on my buzzing noise
After trying multiple grounding points in the car I still had the buzzing. Went and bought a ground loop isolator from maplins, cut the conectors off and soldered it to the lead from the BOSE to the SatNav, it got rid of the buzzing noise but also lost most of the sound! I had to crank the volume up full to hear anything.....aagghh
So, I took the BOSE apart and soldered the lead to the three pins that require you to break the pcb tracks (I did break the tracks). Guess what? It's still buzzing. Not better, no worse!
its amazing how quick you can get the dash apart when you have done it so many times! Let me know if anyone comes up with any ideas.
Cheers
Dave