Hopefully you don't take this as me "talking down to ya', as that ISN't my intention: MY 1st suggestion
WOULD be to pull-out the stereo head (the main radio/tape-deck/CD player, etc) and make sure the antenna wire hasn't come looke from the stereo. That's actually more than likely the problem!
It's not as difficult as it looks, you just have to be gentile. You'll need a special tool that any auto parts store will have-- it's a pair of "U" shaped pieces of metal that go into those four holes on the outer edges of the stereo's face-plate. Some folk' will tell you that you can use 2 pieces of wire hanger but, I wouldn't risk the probability of damage, myself.
Other than that, do you know that radio reception in the area is generally pretty good (judging from other peoples' CAR stereos? Where (generally) are you. I know that here in Atlanta you're guaranteed a clear signal on neumerous FM, and mainly three AM stations-- as ling as your radio receiver is working properly. Smaller communities-- Farther away from broadcast radio transmitters, obviously, get worse reception, than the former.
(I'll just bet that ant wire wiggled its way out of the back, somehow!)
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