Very good chance there's a remote-mounted amplifier somewhere in the car. That makes "testing" speakers impossible from the radio connector. If there is no amplifier, check the two power wires and the ground wire for voltage. The switched 12 volts and the memory 12 volts should have a steady voltage. If you unplug the antenna, there should be no voltage on the ground wire. If there is, the ground wire is loose or corroded and the ground is being supplied through the antenna which is a very poor power ground.
Beginning with the 1998 model year, Ford has refused to sell radio service manuals or parts so you're stuck with the dealer and their grossly over-priced service centers if the radios need repair. GM did that nonsense in 1994. Not sure how that helps the owner but it sure makes a lot of money for the manufacturer.
Jul 5, 2011 at 7:20 PM
