Hello,
I am hoping I can get some advice from some of you "experts" on this forum. I have a '97 Ranger with the 2.3 engine (barely enough power to get out of it's way, but I'm not a speed demon anymore). Last week it started screeching, and I determined the problem to be the alternator bearing. Before I was able to change it, the charge idiot light came on and the gauge showed low voltage. Today I bought a new alternator, switched it out, but to my dismay it is still not charging (idiot light on, low voltage). I took the old alternator to Auto Zone to have them check it, but it passed the tests (it still needed to be changed because of the bearing problem). So now I am wondering if it is a wiring problem, but am not sure where to start.
Here is what I know thus far: With the engine turned off or on, I get voltage at the alternator output wire/terminal, so I know that is not burned out. If I run jumper cables from another vehicle (which is running) to mine, and keep the plugs to the alternator disconnected, I will have 14 volts on the electrical system and no idiot light. As soon as I connect those plugs (even with the jumper cables hooked up to the other vehicle and the vehicle running), I get the idiot light--even with 14 volts on the electrical system.
Because the old alternator tested fine, I am inclined to think that there is a wiring problem, which just happened to be coincidental to the alternator bearing problem, so it is a bit frustrating. Does anyone here have any suggestions? Is there a particular fuse I should look for, or some other troubleshooting test?
Thanks in advance to anyone for help.

 

There is a fuse in the power distribution box next to the master cylinder. If it's blown, the truck won't charge. I forget which one it is, check your owners manual.

 

You might also try getting your battery tested for free at any local parts store, just to ensure that its not the problem.

 

yes sounds like a dead short

 

The battery should be OK. It starts up fine and shows 12.1 volts when turned off, and about 11.7 volts when running 9remember, the charging system is not working). Maybe a dead short somewhere in the field circuit wiring (it should not be the regulator because the old alternator had a working regulator), but I do not know where to look first. I will try working on it more tomorrow. Meanwhile, if anyone can throw out a few ideas they will be most welcome.

Thanks to all for your input.

 

When running the battery should be showing 13.8-15V, not anywhere near 12V. A battery may show it has 12 volts without a load on, but when loaded down it'll drop off quick if something is wrong internally. Get it load tested before assuming that its "OK".

 

im kinda surprised that your alt passed the test, because it sounds to me like a diode is out in it

Matt