1993 F 150 5.0.
Alternator light was on, battery slowly drained when sitting, alternator output was nothing. Voltage on alternator red single wire was 11.5 volts, same as battery voltage after having battery on a charger for a while.
Bought new alternator on the net, put it on and the same thing. Engine running, multimeter red lead to single red wire on terminal black lead to ground. 11.5 volts, alternator light still on.
Thought I must have got a bad alternator.
Sent it back got another one.
Exact same thing as before.
What do I do next to diagnose the problem? I am assuming I did not get 2 defective alternators in a row. but I could be wrong.