I recently installed an Alpine HU and have lost all AM reception. I even had my install shop add an "AM reception booster" behind the radio and still no luck. Is this common with Alpines or aftermarket headunit? Is there an antenna or anything I can add?

 

The most common problem I have found is most USA supplied harness adaptors have a wire missing
There should be a blue wire in the adaptor - this connects to the thin plain white in the factory harness
This wire powers the booster in the factory aerial which is esential for AM
All my adaptors have this wire