I had a factory radio in my 93 f150 xlt, and the left channel front didnt work. I just changed the head unit and it still didnt work, so I decided to replace the speakers. I got the new speaker installed, and still nothing. Any idea how the speaker is wired, and where the problem could be?

 

check the rubber boot that goes between the door and the chassis. The wire may be broken from the flex of opening and closing the door.