Not sure how the 2006 models are, but the newer ones have a thin film FM antenna affixed to the rear window.... close to the rear defroster. Do you have an actual antenna on the hood of your car? If not, it might be coupling going on between the two on the rear glass. Not sure what you can do about it in that case. I would be curious if other owners have similar complaints.

If this is not normal for this year, the other issue would be electrical noise coupling within the electrical system. Probably ground issue. Not easy to find.

I realize I am not helping much but these are the two starting points I would use if I had the car in front of me. :thumbup:

 

just picked up a 2006 E91. So far the wife and i are very happy with it, beautiful car. one peculiar thing i have noticed now that it's getting a bit nippy in the mornings is that when the rear window defroster is turned on, the radio reception goes to crap.

clearly there's some electrical issues there... this is my first BMW, i cut my teeth on a succession of VWs and Audis. before i go n bust up the interior, can someone provide guidance on where to look and any suggestions on the root cause?

otherwise the car is pretty much functionally flawless

Noise in the DC defroster signal'll induct interference to your FM antenna. Prob an ailing connector.

 

My car has a small sharkfin antenna on the roof. sincerely hope i don't have the film atenna as you describe as i would think my only solution is a new hatch glass.... which i'm sure is very cheap.... right?? RIGHT?!?!?!

only noticed it the other morning, so much investigation yet to be done.

 

My car has a small sharkfin antenna on the roof.

The shark fin houses the satellite and telephone antenna. The FM antenna is in the liftgate.

Is the rear-window defroster the only accessory that causes the problem? What happens if you turn off the defroster but turn on as many other electrical loads as you can (e.g., seat heaters + headlights + HVAC blower to max + wipers)?

 

The sharkfin is not the radio antenna.

The sharkfin is not the radio antenna.

http://www.e90post.com/forums/attachment.php?attachmentid=334282&d=1260829447

 

balls. ok, will take a close look at things to see if there's anything obvious. my guess is though that glass will not be needed as if the antenna was pooched, reception would be bad all the time... hopefully "just" the filters or bad grounding or sumsuch deal... damned electrons not following direction!