Antenna cable

I was cleaning up the wiring behind my radio and ash tray and noticed a thin black wire coming off the antenna cable that plugs in the back of radio. I was wondering if that is a AM wire or does the antenna cable take care of both AM/FM. The reason I inquire is that thin black wire wasn't connected and my AM reception is poor for my radio.

The thick black antenna cable serves for both am & fm reception. There maybe a thinner black cable coming off it - that is a ground wire. AM reception may not be too good on some 928 cars not due to the radio but to the condition of the antenna found in the car.

yes, IIRC the thinner wire is a ground.

The larger wire is co-axial and serves as the antenna connection for both am/fm frequencies.

Some cars have the antenna built into the windshield and if its been replaced its possible the antenna is not there or not coneected.

what year car?
The winshield ants have an amp under the dash near windshield on right side that needs to be powered, else bad reception too.

Most all 928's have an antenna amp and most all of them are dead by now, hence the terrible radio reception most all of us experience!

Not me.
Pioneer and JL all the way