Ford Ranger Altenator

Do you have a parasitic drain? Also you need to do a ground check on the positive and negative side of system. Voltmeter is all you need.

Have you checked fuses?

What exactly is a Parasitic Drain?

Fuses are all good.

Parasitic drain - when a circuit in car drains battery while car is off. Modules don’t go to sleep or you have a short in a circuit and it slowly drains battery. 50 miliamps is max drain allowed during key off after modules go to sleep. My experiences with customers has been when a car has a parasitic drain and the battery is low, when you do get car jumped or it starts, the alternator has to work too hard bringing that battery up to spec that it ruins alternator.

Also some Fords only work with a Motorcraft alternator due to it being ECU controlled. Have had many in my shop like that. Recently a Ford five hundred

Was it a New alternator or a remanufactured one? Reman's sometimes are bad right out of the box. Have it tested before you start going through the wiring.

It was a Remanufactured one from Advance Auto.

I never buy remanufactured alternators, starters or master cylinders. I also use Denso starters and alternators when possible. They are expensive but they last. Outside of my customers, I have only replaced 1 Denso alternator in 34 years in my personal vehicles. Never yes never had a Denso starter go out. Most of my cars have 250K and are 15-20 years old.