2009 4.0 new battery and alternator. B+ on alternator reads same as battery. Check all fuses in cab and under hood. No blown fuses. 3 wire connector to alternator - one wire has 12v all the time the other has 0 when key off and 12v when key on and when engine is running. Battery seems to be holding at 12.2. Do you think the PCB voltage is too high?

 

Welcome to the forum

Good testing

On a 4.0l the 3rd wire on the 3 wire connector is purple, it needs to be plugged into the back of alternator on a single spade terminal, thats about the only thing you didn't mention

Key OFF
If B+ reads battery volts and Red wire on 3 wire connector(unplugged) also reads battery volts then the fusible links are OK
The Grey wire should be 0 volts key off then battery volts key on
All wiring is OK
3 wire connector plugged in and Purple jumper plugged in

Start engine
Test battery voltage, should be 14v +
If not new alternators is bad, FOR SURE, not a guess
Actually getting more common for alternators and starter motors to be dead "out of the box"


The Microprocessor sounds cool but doesn't really do much, lol, if you have 12v on the grey wire with key on then its working
You can look at fuses 9 and 10 but they will be OK

 

the purple wire is jumped out to the single connector. I got a new alternator from auto zone. Installed it and voltage would falls pretty fast. Took it back to auto zone got a new alternator because the new one failed so they replaced it and installed 2nd new one and now having the problem I am having now. Returned that alternator and got a Motorcraft alternator from a different store. Still same problem. So I am on my 3rd new alternator

 

2009 Ranger doesn't have the "smart charging" system like newer vehicles, just FYI

Shouldn't be having these issues if the 3 wires test as OK, charging systems just are not that complicated, so we are missing something

Did you use the alternators metal case as the ground when testing voltages?
Also use battery negative to make sure there was no difference, should be exactly the same

Does the Battery(Charge) Light on the dash come on with Key on?
And does it go off after startup?

Long shot would be corroded connection at one of the fusible links or connection at engine fuse box
I would expect to see a slight voltage drop, i.e. battery volts 12.35v and B+ 12.25volts, so not an exact match
Volt meters have very low voltage draw, under 0.02 amp
But when alternator tries to send 35+ amps out the connection heats up and shuts down
Its a pain to find the Fusible links on some models, but that's all I can think of

Try this test
Unhook B+ wire and tape it off so it can't short but leave a little bare metal to test
Start engine
Test B+ terminal voltage, should be 14v+
Test B+ wire voltage, should be battery volts exactly, so test battery volts engine running, this B+ wire voltage is the Red wires voltage on 3 wire connector


An alternator will drain the battery if its left on all the time
The Grey wire(green wire on older rangers) is the ON/OFF switch for the alternator

Grey wire is also the Battery Light circuit
An alternator multiples voltage by the engine spinning the rotor
The rotor is sent voltage by the Voltage regulator, this voltage is from the Grey wire, so no volts on Grey wire = alternator off
You could spin an alternator forever and without "startup" voltage from the grey wire it would just spin and spin, no voltage out

When the voltage regulator send 9volts to rotor it causes a magnetic field to build up around the rotor
As the engine spins the rotor the spinning magnetic fields cause the 3 Field Coils in the outside case of the alternator to generate AC Volts, AC is converted to DC by Diodes and you end up with 14volts out at B+

The Red wire on the 3 wire connector is the Monitor Voltage for voltage regulator, it uses this voltage to set Rotors voltage, so it may send rotor 8volts to lower output voltage or 11volts to raise output voltage based on Monitored voltage, these are just general numbers, not specific

Back to the Grey wire
When you turn the key on the Battery Light bulb gets 12volts(battery) from fuse 9 on one terminal, the bulbs other terminal is the Grey wire at alternator, and alternator is at 0 volts, so its in essence a "ground" and Battery light bulb lights up(voltage regulator is sending this voltage to rotor so current is flowing thru the bulb)
When engine is started(and alternator is working, lol) then fuse 9 is now 14v AND the alternator/voltage regulator is now 14v, so both terminals on the bulb are 14v and no current flows thru the bulb and it is now off

 

I am getting .41 on B+ on alternator when disconnect battery cable from alternator when running
battery + to - 12.53
alternator cable connected b+ to case 12.53
purple wire to battery + 12.43
purple wire negative -.0029 key on and key off
red wire 12v all the time
grey wire 0v when off
grey when on 12.53
did check both fuses and they are fine
battery light stays on when key on and when I start the engine
could something be wrong with the cluster?
should the grey wire be lower voltage to call for alternator to push more voltage?
could their be something in my system that is burning out the alternator?
I just don’t understand how I am on my 3rd new alternator and none of them are working?

 

3 wire connector Red wire is 12.0v and battery is 12.53v?

Then Red wires fusible link has corroded/bad connection

If you want to test for that have volt meter connected to Battery so you can see the voltage
Start engine
Use a Jumper wire from B+ to red wire
Should see voltage jump up to 14+ volts
Confirms Red wire voltage fault

 

You were 100% right. Jumped the red wire to the alternator b+ and shot right up to 14. Now where is the fusible link so I can replace it or how do I repair this?

 

Yes, B+ and Red wire are connected together at the one end of the larger fusible link, so should be exactly the same voltage, and exactly the same voltage at battery
You found the problem, good work

Unusual problem but does happen
No, I do not know where in the harness they are
Could be at alternator end or battery end of the harness
Battery end of harness was more practical/common

Disconnect one battery cable before pulling back any harness loom covers
You should be able to find the B+ larger red wire at the engine fuse box end

Look at the diagram
Follow the larger B+ wire into its harness
Dark Blue/Light Green 10ga fusible link goes to Battery positive/fuse box and a Brown fusible link that goes to red wire on 3 wire connector

Brown fusible link(4.0l engine) is the issue but most likely just the connection not the fusible link itself, but can be

Fusible links will have a rubber marker like this: https://www.ford-trucks.com/forums/a...1&d=1496604608

Or this: https://m.media-amazon.com/images/I/...1000_QL80_.jpg
Without the eyelet of course in this setup, just a crimp connection usually

The harness uses split loom so can be un-taped and the loom is slit so can be pulled back exposing the wires

 

You are right again. The fusible link was fine, but the wire broke that feeds the fusible link. What a bad design, to bury a fuse in a wire loom. Thanks for all the help. I really appreciate it.