My 2001 A4 w/Bose speakers has 4 signal amplifiers, one inside the 4 corners of the rear window. Each signal amplifier is 1" by 2" and they are different colors.

A sample on eBay is:

http://www.ebay.com/itm/Antenna-Signal-Amplifier-OEM-8D5-035-225-K-99-01-Audi-A4-A4-quattro-/300899744863?pt=Motors_Car_Truck_Parts_Accessories&fits=Make%3AAudi&hash=item460f05bc5f&vxp=mtr
Does anyone understand why there are 4 of them? How does the system work? Is it known which is the AM and which is the FM?

I had issues with the many wires to the window cut when the glass was removed. I have re-connected each wire including some soldering and some Frost Fighter defroster tab bonding, here:

Frost Fighter 2000 Defroster Tab Bonding Kits

The last problem is the AM is weak. I may miss Dave Ramsey!

Any information?

Thanks,

John