2007 Ranger 4x4 4.0 automatic. Battery light came on, so I had Autozone test. Said battery was good, alternator was bad. Replaced with reman alt, and charged battery and the light went off for one day, then came back on. Went back to store, tested and alt only putting 11 volts, took alt off and put on their inside tester, and it failed. So, I put on another reman alt and charged battery, and the battery light is still on, and alt only putting out 11 volts. Could my truck be causing these new alts to go bad, or do you think they are bad from the start? The guy at Autozone says I need to look for a bad fusible link in the alt wiring.

 

Have them Bench Test the replacement alternator before leaving the store with it, kinda sounds like a bad batch of work.

 

Just took it off and took it back and it bench tested good, had them do it 3 times. I put it back on and tested the output myself and got 12.5 volts at idle.

 

Ok good, so now we know this one bench tests ok. SO, now run the rpm up to say 2000 & see if output rises under load, meaning with all the lights on, cabin fan on High speed, cigar lighter pushed in & see what voltage you measure across the battery posts. At rpm it should rise to about 14.3-4 or so under load.
A poor ground, or corroded B+ or B- battery cables can cause voltage drop across a connection, so if that's the case, you could do a feel test of the cable connections to the battery posts, alternator B+ & engine & B- ground connections to the engine & alternator to see if any feel warm or hot from excessive resistance. Then use your multimeter to perform a under load voltage drop test across the suspect connection.
Since we only have 12 volts to work with, it doesn't take much resistance from loose, corroded, broken wire strands or the like corrupt electrical connections to cause us woes.

Did this problem come about slowly over time, or suddenly after some event?

 

The battery light just came on for the first time a couple days ago.

 

At rpm with lights, radio, fan, and defroster on, got only 12.11 volts at battery. Could not find any warm cables or wires.

 

Ok, well the AutoZone guy is likely right in suggesting you check the alternator fuseable link, as it supplies power to the alternator field coil, so if the link is blown, or has gone high resistance for some reason, the alternator won't have any output.

 

You can go here BBB Industries- Premium Alternators, Starters, Power Steering Products and Turbochargers | TSB's & Wiring Diagrams click on Wiring Diagrams, enter your vehicle particulars to look up the electrical pictorial for the Battery / Alternator wiring which will include the alternator contacts for the two fuseable links, the one that connects the regulator to the field coil & the other one that protects the B+ wiring between the alternator & the input to the under hood power distribution box on the drivers side. The schematic shows the links close to the alternator external connections, so should be close to the wiring harness/connectors that connects to the alternator. You might have to unwrap some insulation to inspect the fuseable link to see if its blown. If you have a multimeter you could test for B+ on both sides of the link to see if its blown / open circuit.
Let us know what you find.

 

At 12.11 volts, your battery is between 50-60% SOC, so put that puppy on a low rate of charge, say 2-4 amps on your smart charger & let it slowly recharge the battery overnight, it'll appreciate it.

 

Thanks, I will look for the fusible links tomorrow.

 

I don't think that the fusible links are bad. With key off I got 12.4v at the stud on back of alt, and 12.4v on the red wire from the 3 wire plug on alt. With key off I got .1v on the gray wire from 3 wire plug, and with key on got 12.2v. So, if I understand correctly the fusible links and wiring are good and the alt is bad. But the alt bench tested good. Any suggestions?

 

Tell us how a bad alternator could bench bench test ok 3 times!!! What under load output voltage did it bench test at?

 

It sounds like fuse link A is ok.

Try disconnecting the alternator electrical connector & testing for B+ to a good clean, unpainted ground, (or the Battery B- post if your test lead is long enough) at connector pin #3, its the alternator field fuse link.
If you don't have B+ battery voltage to a good ground, the fuse link is blown, or something is wrong with its wiring, or splice connection/s.

Right now with no alternator output, it seems fuse link B is blown, or has become high resistance for some reason, because you don't have any alternator output.
If fuse link B blown, or its wiring is damaged or its splice connection has become corrupt/high resistance, the alternator stator field can't self excite, so if no electon flow through the field coil, it cant make a magnetic field for the alternator rotor to rotate its windings through, thus the alternator can't produce any electrical output.

Get the battery on a low rate of charge, so the cells don't sulfate & weaken its CCA. As we've plenty of cold winter remaining, you don't want the battery to lay down on you when you need that puppy to crank the engine.

 

Found the problem! Read online that someone had the same problem and it turned out to be a wire rubbing on the inner fender beneath the battery tray. So I checked it out , and sure enough a red wire was rubbing on the edge of the inner fender, and was almost cut in half. I spliced in a new piece of same gauge wire and started it up and now have 14v output from alt. I also sliced a piece of extra fuel line I had down the middle and put it on the edge of the inner fender to prevent further rubbing.

 

OK, good find, fix, feedback & to hear all now seems well & your on the road again. Any chance you can take & put up a photo of the area & fix?