I have a 92' Bronco Eddie Bauer with a 5.0L. The battery died so I had the alternator tested and it failed. I replaced the alternator and yet the vehicle is still not charging. I had the new alternator tested multiple times and it passed each time. I read on a forum about a TSB to replace a damaged plug to the alternator. I replaced this plug today and yet the alternator is still not charging. The vehicle runs but when I remove the negative cable it dies. Cables cleaned, otherwise vehicle runs well. Dash gauge reading very low "normal". Any help would be appreciated before I turn it over to a trained professional.

 

I don't have the details on it's location or specs but it sounds like the fusible link is open. I think that it is between the alternator and the positive post on the starter relay/solenoid mounted on the fender by the battery.
I hope someone with more knowledge chimes in with more information.

 

Thanks Dave for the help, I really appreciate it!

 

There should be a larger wire coming off of the alternator, that's your charge wire. At idle, the post on the alternator that is connected to should have 13-14.5 volts, test that. If that is good, test the resistance of that wire end to end to check continuity and general wire condition. Remember this only checks for an open circuit, a voltage drop test would be another good one for this wire to check condition. I think your system uses a wire that gets a signal from the ignition switch that the key is "on" so the alternator knows when to start charging. If this is the case, check for a signal whether it be the wire is grounded when the key is on or it is providing battery power when the key is on I don't know off hand, but I'm pretty sure one small wire does that and the other goes to your gauge. The big wire should have the same voltage coming off the alternator as the positive terminal on your battery. Bust out that multimeter and let us know what you find!

 

Great advice , just make sure your battery is fully charged and good(or new)The battery will cause problems ,dead cell, low amperage /voltage etc. Also make sure to disconnect the wires before u read them (multi meter).Our alternators spin making ac voltage(armature) and they have diodes in them to change that to dc voltage .I have had the diodes go bad killing my battery(low drain).The fusible links can go bad opening up. I think you can trace that wire from the alt to the solenoid, And as stated make sure all your connections are clean and rust free . As our truck age and get rusty the ground becomes loose, weak rusty providing problems. Good luck!!!TR

 

First off, don't do this: That is a 1960's era test idea, long before vehicles had expensive electronics. Don't do it.

I'm pretty sure a 1992 will have the infamous "2G" (2nd Generation) alternator. They are known for starting fires. We came real close to losing a car with one. Son was trying to locate a socket and driver to undo negative battery cable as fast as he could, while I was using an old towel to attempt to put out plastic burning, driven by a white-hot arc on the 2G alternator's output receptacle. The plug was just burning goo. And it was a new plug pigtail, as part of a replacement new not rebuilt alternator installed maybe 2 years before that. The harness, and all plastic around it was on fire, and spreading very fast. With airflow under the hood as a car/truck is being driven, fire spreads very fast.

The 2G alternator is a mess. Instead of a big stud on the back of it for output, with a ring terminal on the wire to battery, the 2G does everything via plugs. The plugs blade conductor size is just too small for a good reliable low-resistance connection over time. Originally, it was thought that the socket's fingers relaxed over time, causing the problem, which is why the alts were sold with a new harness connector to pigtail. But that wasn't it.
Also, the car had a another plug connection in the wiring, in series with the alternator output, on the way to the battery. Don't know if a Bronco would have that plugged connection or not. It had two wires in parallel from alt output plug, through series plug (using two contacts) heading for the battery and 12 volt inter tie over by the starter relay on the fender. It was a 1990 5.0

We bought a new 3G alternator, for 1995 Mustang, I think. I had to drill one size larger one of the mounting sleeves of the new alt, had to clock the front/back halves of it so connections would be reachable, and built a new harness with ring terminals, new regulator plug, etc. etc. A crash course in one day, as the car was headed off hundreds of miles to school the next day!
If it would have caught fire one day later, it would have happened on an interstate, so the car would have been burnt to a cinder.

After you locate your problem and fix it, think real seriously about doing a 3G upgrade. Many articles/posts on doing it.

 

Even if you swapped in a 3G you need to verify there is power on the Light Green/Red wire when the key is in the Start/Run position. This is the "exciter" voltage to turn on the alternator.

For reference: