Fostang -- First, check and verify that the light isn't telling the truth. With the engine running, check the voltage in the battery with a multimeter. There should be about 13.5 - 14.5 volts in the battery. 12.5 or less and the juice from the alternator is not getting to the battery through the wiring harness. 14.5 + and the battery is overcharging. That would suggest your new regulator is faulty. Don't worry, sometimes bad ones make it out of the factory. If you can find a known good regulator, swap it out and check again. You may have a pinched or short wire somewhere in the harness otherwise. That's a PITA (Pain In The A--)! I think some fords actualy had a resistor that worked to keep the light off. If the resistor dies, the light will ground and turn on. If you still can't get it to work, you can always bypass the harness, get a chevy alternator and run a straight wire from the stator to the battery. That's an old racing trick a friend used when the wiring harness caught his 5.0 on fire and he had to rewire the entire car. Just some food for thought.

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Pony Express 66
God Speed and keep it between the lines!

Just like you said it was the harness. A faulty connection. Oh and the "NEW" altenator didn't work either. Up and running now no problem!!

Glad to see you got it fixed!