Charging problems

[Danax87325]

1987 325.
I had a short in my positive battery cable (battery mount is missing allowing battery to slide which wore a bare spot on the small wire of the positive battery cable in trunk), which I fixed, but my alternator is still not charging. Did the short fry something? Alternator tested 12.2 volts at idle (Autozone guy).
Dash bulb does not light when key is turned to the 2nd click but does sometimes, when the car's running!
Before I go out and buy another alternator, do any of you have an idea what has happened here?

[jlevie]

A shorted primary power connection could cause failure of the alternator. But a bad alternator/battery warning light bulb will prevent the alternator from charging as that bulb is the source of exciter power. A simple check of the exciter circuit is to ground the exciter (small) wire at the alternator. Then turn the key to ignition on. If the bulb lights the exciter circuit is good and the problem is in the alternator. If the bulb doesn't light there is a problem with the bulb, cluster, or wiring.

[Danax87325]

I appreciate that answer. I haven't put a test light to the exciter terminal of the alternator yet (I'm at a friend's house with only some of my tools) but noticed that the alternator indicator bulb, along with the parking brake indicator bulb and brake fluid bulbs all share the following symptoms;
1) Aren't lit when key is turned to the fully on position.
2) Are dimly lit when the car is idling, but go off when RPMs are increased sufficiently.
3) After the car is started then the key is turned off just enough to shut the engine down but without leaving the "on" ignition position, the lights will be fully lit. If the key is turned one click off, then the lights will not light up when turned back on, although occasionally they will.

What might these clues mean? My ground strap from the alternator is tight although greasy. I'm about ready to pull the cluster and check for something causing such strange symptoms.

[Gregs///M]

Verify your Engine to chassis ground cable is secure and in decent shape. This cable is one of the most important cables in your car. It closes the ground loop for all the engine electronics to the chassis, which returns power to the battery.

This can lead to starting, charging, and other electrical problems due to poor grounding including cluster problems.

Check out my signature for the differences between a poor cable and a new one.

[Danax87325]

A shorted primary power connection could cause failure of the alternator. But a bad alternator/battery warning light bulb will prevent the alternator from charging as that bulb is the source of exciter power. A simple check of the exciter circuit is to ground the exciter (small) wire at the alternator. Then turn the key to ignition on. If the bulb lights the exciter circuit is good and the problem is in the alternator. If the bulb doesn't light there is a problem with the bulb, cluster, or wiring.

UPDATE: I finally took your advice and grounded the exciter lug and, sure enough, the charge indicator lit every time. Seeing how my voltage measurements kept changing when I would start and turn off the car, and how the indicator light lit sometimes but mostly didn't, which indicated something like a short or bad connection inside the alternator, I decided to pull the voltage regulator and check the brushes. Sure enough, they were down to almost nothing and were uneven. I bought the brushes for $3.49 at O'Reilly and replaced them per this thread http://www.r3vlimited.com/board/showthread.php?t=230068 and VOILA, 13.58 volts at the battery with the car running. Hopefully I'm good to go. Thanks for the assist...