E320 AM radio antenna cable run?

[sailer]

I have an 99, E320 which I purchased from MB Leasing Corp. about six months ago. Everything fine except for one thing. There is no AM antenna signal getting to the unit in the dash. Radio itself works fine as prooved by strong signal when in proximity to AM radio transmitter sites. Only one or two stations are picked up. The antenna is in the rear window of the vehicle. There is an empty space, with bracket, that could have held a device over the left rear wheel well in the trunk. Would this have been for a CD deck or was there some sort of active antenna amplifier used in this system? Is there some kind of hardware missing? How does the cable run go from the rear window antenna up to the unit in the dash? The FM portion of the radio is fine. But I would really like to have my AM working.