hello - I have an 05 S4 Covertible. Sympony Radio. CD and Satellite works fine but AM / FM sounds as though the antenna is not connected. I've heard about an power antenna booster, but can't seem to locate it. Some have said in a convertible, it's in one of the C pillars. Not sure what C Pillars are.
Any help on finding and testing this device greatly appreciated.

 

99% sure its in the trunk lid...

also pretty sure that won't fit your problem. the new issue were finding w/ Cabrios is the wires are breaking apart in the plastic piece that carries the wire from the trunk to the radio. and the repair we are offering is a wire overlay from the booster to the radio. its currently NOT covered under warranty and were charging 8 hours of labor to do it.

hope this helps

 

and a C pillar in a convertible would be inside the top... which is impossible, So the "some" are very wrong... its not even in the C pillar in a Sedan, its attached to the rear glass under the roof trim.