Here's some advice from someone who has battled the Battery light on 3 separate Ford products, a Taurus/Sable/& SHO, and won each time. After screwing around with alternators, I finally figured out what was really happening. On top of the alternator there are 2 factory connectors that attach directly to the alternator and then jump over to the frame above the radiator and become part of the wiring harness. One of the connectors is large (with 3 or 4 wires) and one is smaller (with 1 or 2 wires). After years of driving your car with the engine rocking back and forth on the mounts, the braided wires in these connectors or near the connectors break inside and cause an intermittent loss of alternator charging. This starts out as a flashing Battery light, and eventually ends in the Battery light staying on all the time. At this point, the alternator stops charging the battery, and pretty soon you will not be able to start the car. In all 3 cases, the broken wires were in the smaller (1 or 2 wire) connector wires. I have a 1993 SHO which uses a Mitsubishi alternator- therefore the connector wasn't available at Ford. So instead, I cut the connector off the wiring harness about 3 inches back and took the connector apart and replaced the wires. Then I reattached the connector to the wiring harness and now its good as new. If you want to conduct an easy test to see if what I explained is happening on your car, take 2 clip leads (alligator clips) and attach one end of the clips to the 2 terminals inside the connector on the alternator and then shave the insulation off the wiring harness about 3 or 4 inches back from the connector and attach the other end of the clips there (make sure you attach the clips to the right wires though! otherwise the car will not start!) If I was a millionaire, I would bet you a million dollars that this will end your Battery light problems. As a final note, a guy I work with owns Mazda's clone of the Ranger pickup- and I diagnosed the same thing on his truck too.
