Well this is a first. Over the past 16 years I've owned five 12A 1st gens (all GSLs, two of which we still own) and had to replace the alternator a total of four times, usually due to the voltage regulator (located inside the alternator on these cars) calling it quits.

The typical symptoms when this happens is an unusually high voltage reading of somewhere north of 15 volts indicated, which is soon followed an unusually low voltage and the warning light coming on. At that point I have less than 1/2 hour to drive to a rebuilt alternator facility before the battery (and engine) dies.

But today was different in a wierd way:

First, the voltage reading was around 14 volts, but the guage oscillated all over when I hit the brakes (brake lights) or used my turn signals.

Second, the turn signals (both right and left) flashed at twice the normal rate.

Third, when disengaging the clutch and letting off the gas as I approached red lights the tach would start to drop toward idle and then blip up to 3K momentarily (as I touched the brakes) before settling at idle--- even though the engine rpms did not blip at all but continued to settle toward idle rpm as normal.

The strangest thing is that it did this all the way from work to the insurance office, but after I got back into the car to drive home the problem completely went away!

I could be wrong about the regulator since I've never seen an intermittent voltage regulator failure before, but has anybody else ever experienced this? If so, what did it turn out to be?

 

My gauge bounced around when turn signals were on and brake lights were applied and I ended up replacing the alt. The problem is still there so I am thinking it is a bad ground. Could it be that possibly a ground wire came loose or is now so oxidized that it is finally causing problems? Just a couple ideas I am throwing out there.

 

My car acted pretty much like that when I lost my main fusible link. Fast turn signals, voltage spikes indicated with brake/turn signal use, and (weird) my headlights got really bright and the car felt stronger than usual. Ran like that until I got to work, then of course it wouldn't start when it was time to leave. Sorry for the ramble, obviously your issue is not the fusibles.

 

battery cables

 

This is actually encouraging, since it indicates that the voltage regulator may not be on the fritz after all. (Symptoms have still not returned btw).

On the other hand, I did have my main fusible link out a week ago to use it for diagnosing a problem on the GSL I was about to buy for my wife. It's possible that I didn't re-insert it all the way, so I'll check on that tomorrow.

Meanwhile, I have a stash of emergency fusible links (scavenged from auto wreckers) that I keep in the car at all times.


As for the battery cables theory, those are clean and in excellent shape. (and how the hell would that cause these problems to begin with?)

 

That's happend to me too, I put it on the fusible link due to the fact I blew it, the main, and twisted it back together until I found a replacement. One day just normal driving the same, exactly, thing happened as you discribe and I looked threw all of my connections and "retwisted" the main link and didn't have a problem again.

 

Could be a bad connection in the positive side of the system.
When you have the symtoms, disconnect the negative battery terminal, and reconnect it.

If the positive is disconnected, and reconnected(bad connection) it "may" cause the problems you have described.

 

Well, the problem returned today and this time it wasn't intermittent. I had already secured the fusible links so I knew that wasn't the problem.

When I shut the car down and tried to re-start it sure enough, there was no battery power available. None. The terminals looked clean, but removing and inspection revealed hidden corrosion between the inside of the clamps and the battery posts. So I stand corrected, and thanks for all the tips.


I quickly removed and cleaned the battery cable clamps and this proved to be the cause since afterward all was once again right with the world.

This is a problem that I'd encountered and diagnosed dozens of times over the last quarter-century, but the first time I'd ever seen advance symptoms of impending loss of contact and intermittent glitches caused by this.

 

Glad you got her figured out man! Thanks for the update.