Xubydoo

Hi All,

I have been finding useful info on this forum for a while, but this is the first time I couldn't find an answer, hence the post. My vehicle is a 2006 a6 (c6) avant with the bose sound system. Any help would be appreciated.

Here are the symptoms:
The radio was working fine until I had a MMI crash, and the radio could only receive very limited FM signal (3 channels) in town and no AM signal.

Here is what I did diagnosing the problem:
Connected VAG-COM, it logged 2 radio faultsI checked all the connections on the amplifier Part# 4F9035225D and Part# 4F9035225A, and all the continuity checked out from the amplifier to the antenna. (these part numbers for the amplifiers are different between the sedan and the avant, since they are shaped and mounted differently, one on the lower driver side and one on the upper passenger side on the avant)

Checked the shark fin, it is a little wet under the shark fin mounting hole, but continuity checked out as well.

Checked fuses, there is a blow 5A fuse at location 21 in the driver left side fuse box for the amplifier. Awesome, should be an easy fix, but replaced it with a 5A fuse and everything is exactly the same. Tried to clear the radio fault code but it immediately came back.

Tried to run the radio for several weeks, that fuse was never blown again.

OK, so since the wiring continuity from the amp to the antenna is fine and fuses are OK, I turned my attention to the amplifier itself. 12V going into the amp is good, so I replaced both of the amps Part# 4F9035225D and Part# 4F9035225A, one at a time, but that did not fix the problem either.

At this point I tried to check the signal difference using VCDS, and the reception did not change before and after I pulled the amp fuse. So I guess it is some issue between the amplifier and the radio. I have torn apart the entire trunk section of the car, so I really don't want to tear up the entire car to just keep randomly tracing the problem. So I would really like to have some pointers at this point.

I could alternatively take it to an audio shop, but they couldn't promise anything either.

Any help would be appreciated! (images are the 2 amplifiers from google)