Went to first car show of the season today, anc the car was nothing but trouble.  Luckily the show was at my friends firestone shop, so they helped out....

On the way there, I was losing voltage (have a volt gage under dash).  Car would charge, then Id hear a pop & screech, then it would start to lose voltage.  Car kept running, but eventually got to the point of no lights. gages, etc.  Occasionally would come back up, then id hear a quick screech, and same thing again.  So I figured alternator, right?  (car has a 1-wire alternator in it) Not so fast....

So we swapped out the alternator for a new one (2 actually), and it still doesnt show charging (yes, internal regulator, so that should be new too).  He load tested the battery and it came back bad (about 140 cca under load).

We put enough of a charge into the battery to get home (barely) and every once in a while on the way home, id have the same quick screech with the new alternator, and towards the end the engine would cut out when it did it.  got home (with a lot of prayers on the way!) and the battery showed about 9v.

For kicks, I tried disconnecting everything non essential (pwr top wire, stereo, etc) and had same results.  Checked and have same batt voltage at bacl of alternator with power off.

My friends theory is that the battery has an intermittent shorted cell, and thats what the problem is.  I could buy that, but I cant get my head around why the alternator wouldnt show charging?  Does his explaination make sense?

Alternator is wired with output cable to the + on starter solenoid (and has been for years w/o problem).  All good grounds, all wires are tight and in good shape.  At this point, I cant think of anything else it could even possibly be, but ???  Am I missing something, or would a bad cell cause this?  Like I said, we tried 2 alternators with the same result....  Any thoughts or anything else to check before I buy a new battery?

THANKS!

Also when running, if you were standing next to the car, you could occasionally hear what I would describe as a faint electrical crackle prior to the screech sound...and it sounded like it was from the battery area.

The battery tested bad.  Replace it.  If there is still a problem, it is there whether the battery is old or new.

A little clarification:

I didnt hear any weird noises with the "new" battery.  however, I also didnt run it too long with it in there, since it wasnt mounted well, etc.

Volt meter at the battery terminals read 12.4v while running; 12.5 while not running. 

Reading on the volt gage under dash has been/is consistent with voltmeter at terminals

Belt has been tightened/retightened

Revving engine to >2k (in an attempt to get alternator to kick on) yielded no change

Gage array under dash is fused; would have thought that would have blown if there was a short?

Previous to all of these problems, the gage under dash would regularly start at ~12v, then when the engine is revved to above about 1200, the needle would kick up to the normal 14.5, and would stay there until car is shut off.  Because of that, im skeptical that it doesnt kick on because the battery is fully charged?

All wiring in the car was new 8 years/about 17k miles ago

Is it possible that the bad battery killed the new alternator on the 25 minute drive home?

I once had a Sears diehard that one of the cells reversed it's polarity.  The guy at sears checing it didn't catch it, but I did.  He got a negavive reading on that one cell, so he reversed his probes and proclaimed it OK.  I called him to task on that, and they replaced the battery.  Anyway, if all the cells got reversed, it would knock out the diodes in the alternator.  Is it possible that the battery got charged backwards at the show?  Or jumper cables hooked up backwards?  Either one would trash the diodes.

Interesting thought.  Im not 100% sure about that one.  If I had to guess, Id say probably not likely, as I tried to keep an eye on them while working on the car.  Im really paranoid about the metal retainer around the top of the battery, so I usually watch pretty closely the few times someone other than me works on the car.  I never saw them hook up anything backwards, but that doesnt mean it didnt happen.

Im thinking through the original failure again, trying to figure out the issue.  I had been hearing the "screeching sound" (very shourt duration) for the last few weeks.  it was usually upon heavy acceleration - if I let off the gas abruptly it would make that sound.   I originally thought it might be one of the bands or a pump in the trans, it was that consistent with letting off gas/upshifting, etc.  However, alternator belt was/is tight, so not a slipping belt.

On the way to the show, I realized there was a bigger problem because occasionally the radio would crackle for a split second and drop out.  At that time I started watching the gages, and they would intermittently go dead for a split second, then come back up whenever I heard the screech sound (IIRC).  It all happened in an instant when it occured, so not sure if the sound came first, then dead needles, or simultaneous, or what?

Over time (about 25 minutes of the drive) it got more into the mode of bleeding down voltage, hear the screech, then volts would jump back to 14.5 for a brief time, then drop to 12 volts (I assume thats when the alternator stopped working) then bleed down voltage to 8-10 (assume thats when it was draining battery).

When tested, the battery only showed capacity of about 140 cca.  Showed 12 volts without load, dropped to about 7-8 volts while trying to crank.

When I had problems on the way there, it was with all circuits.  I.e. under dash gages, stereo, lights, brake lights, turn signals, heater motor, fuel gage, etc.  Thats what makes me think it wasnt a short, as that would have popped one of the inline fuses i have (or circuit breaker under the dash for the convt top circuit), and then id think that only one of the circuits would have been dead?

Im just stumped; the 1 wire alt is so simple, I didnt think even I could screw it up; guess I was wrong!

THANK YOU to all who have offered ideas on this.  I cant tell you how much I appreciate it.  As you guys probably know, its almost impossible to find people who know how to une a carb or really troubleshoot problems vs. just replace parts!  so THANKS!!!!

One more thought.  Is the main feed wire from the alternator to the battery grounded somewhere?  Do you have an ammeter?  It could have an internal ground also.

Thanks to everyone for the help; Ill post again once I get some parts and go next steps!

Thanks!!

Ron

However, while the car was running, the starter engaged for a split second.  happened twice.  Im thinking I also need to replace the solenoid.My suspicion is that I messed it up last year when I modified it.  On the + battery post of the solenoid, there was a retaining nut at the base of that stud.  I added a wire for a stereo amp, and to get it to fit, I removed that nut, and just piled the wires on and tightened the end/retaining nut.  I wa never really happy with that, but never got around to coming up with a better fix (still not sure what Ill do?).  My guess is that knocked something loose inside that casued the starter to trigger, especially since I undid that nut and removed the stereo amp & power top wire to rule those out as culprits for other problems.  This is really the first time Ive run the car like that, so my guess is that I knocked something loose or something inside.  Would that make sense?  Hope im explaining it right.

So my guess as to root cause of the charging problem is that I had a shorted cell on the battery.  That *may* have cooked the old alternator.  all subsequent alternators (except the oni I just put in) were the wrong ones - they were 3 wire vs. 1 wire.)  Does this make sense, or am I missing something?

BTW, wiring harness is in good shape/about 8 years old, and the ignition switch was replaced last year.

Thoughts??

THANKS to everyone for the thoughts/help!