DIYbanter - Car Antena problem

BestestWorker wrote:

When the radio is on AM, I can hardly hear my favorite channels. When I touch
the antenna the signal comes in much stronger. I am about 40 miles from the
transmitter. FM is no problem from the same distance.

Other than clipping a wire to the antenna and wrapping it to my wrist while I
drive, is there anything that you can suggest?

TIA

You didn't mention if has always been that way or went faulty in
that manner. Is it a 'factory installed' original or was radio
added or changed since the car was made? What kind of antenna is
it?
If it's always been like that you may find that there is a small
'trimmer' adjustment screw that tunes/adjust for the particular
antenna situation in your car that was never 'set up' right in
the first instance. These can sometimes have a very big effect on
how strongly the signal is received and possibly more so on AM
than FM?
Other than that there may be break in the wire in the cable from
antenna to set. A loose or disconnected plug or corrosion and/or
short circuiting at the base of the antenna. Because of the
higher frequency of FM sometimes these problems can deaden AM
more than FM signals.
More (a lot more) information needed!