I just got my brother a 1986 F-150 with the 5.0L motor. Apparently there's an issue with the wiring harness that plugs into the alternator (the square one). Since it's used, of course the wiring is all f*cked. Someone tried to splice in some new wires without replacing the plug itself (which I understand is the problem). So, I'm looking for confirmation. I put in a new alternator, new battery and new solenoid. Truck runs ok for about 2 mins then goes south and dies. I have a battery/alternator tester hooked up and when it stumbles and dies, I can see that power is no longer reaching the battery from the alternator. I suspect that the alternator plug gets warm/hot and resistance goes up and the truck dies.

It gets even worse if you turn the lights on.

From what i've read, there is a tsb on the 1986-1994 F-150 alternators and replacing the plug (the square one).

I'm guessing that if I replace the defective plug (pig tail) that the problem should be resolved.

Give me your opinion.

Also, if you have a part number for the pigtail from AutoZone, O'reilly Auto or Napa, I'd appreciate it.