I Just put a 95 LT1 back together. New top end and bottom end. I cant keep the car running more then 24 hrs. The car still needs a tune but i think that is not my issue.

This is the 3rd alternator ive replaced on this car in the past 72 hrs and its bad too now! Only getting 13.5 volts out of the alternator and its supose to be around 14 -14.8. The battery isnt new but i load tested it for 20 secs and it held its charge. I had fixed a issue with the alternators feed wire having a break in it. Put the last alternator on with a fully charged battery.


The car not having a tune will cause it to stall ocassionally and when it does the car wont start back up. Battery is dead or low on voltage. The gauge says its Below the middle even when i read 14.7 volts coming out of it. Now the gauge says im getting like 9 volts out of it and its getting 13.5. I tested for a draw I didnt find one. IMO consiquential of the low battery the car will start to start and then slip off the flywheel. Its possible the starter soleniod is going bad as the starter is sluggish.

What could kill a alternator this many times and so fast?
Any help appreciated
Thanks


I just tested the Alternator again and now its putting out 13.9-14 volts. What could be causing it to slowly lose its ability to charge?

 

You got a bad cable or bad connection, or bad ground somewhere.

 

Think ive figured it out. The battery screw left a somewhat loose fit for the positive cable. Maybe that caused it? did about 2 hrs of driving on it and it didnt die. However the battery charging is below the middle mark and on the verge of the red if not in the red. checked power out at the alternator again best was 13.99 and worst was 13.78.

 

sounds like there is another loose connection in there somewhere.

 

If you've got 13+ V at the alternator, and your dash volt meter is near the red, it's not the alternator. It's a problem in the wiring between the alternator and the charging system.

 

First stop right there. Typical is over 14 however the GM shop manual says it should be 13.5 to 15.5. So I see no problem what so ever.
Lets continue.

WTH is all that mumbo jumbo????? You say the battery is dead. Then you give us the value of the voltage when the engine is running????? Which incidentally is a good value. Then you start in about the gage.

What is the voltage across the battery when someone tries to crank the engine???????? This is the useful number that indicates for sure the battery is up to the task or not.

Next point. When you test the output of the alternator, you always check the output at the alternator AND at the battery post (not the connector). This assures you have a proper connection. If you measure a different number at the alternator post then at the battery POST. You have a connection issue.

Another point. A starter is a series of wire windings. Like all wire windings, they eventually become shorted together more and more over time. As this occurs, the resistance of those windings becomes less and less. They then pull more and more current. It then becomes such a huge current draw that the battery can no longer supply enough current to crank it. Therefore the test of the voltage across the battery as someone cranks it over can also determine that. If the voltage across the battery is lower than 11 volts, that could be an indication the starter is going bad. However, it could also be an indication the battery is going bad as well. DON'T GET CONFUSED BY THIS.

Last point. A starter that is going bad but hasn't quite got there all the way, can exhibit a problem at elevated temperature. So your running the engine and the car stalls. Then when you try to restart it, it won't crank. Then the starter cools down and VIOLA. What you do you know, it starts again. Guess what can predict this? You guessed it the voltage across the battery when someone cranks the engine over. Well what do you know.

I don't give a rats hat about the gauge. That is a problem that has to be worked out.

You don't have an alternator problem. It is either the starter, the wiring(including the ignition switch) or the battery. Period.

Get the starter tested for current draw under load. If it tests good cold, heat it up with a blow dryer or the sort and retest it. If that's good, have the battery tested PROFESSIONALLY. Incidentally, don't let the same I(!*TS that keep giving you alternators do the tests. Go somewhere else.

 

Thank you for the list of ideas. I tried to be clear on my post with my information reguarding the issues. Sorry if i had any unclear information.

The Last Alternator was bad( thats number 4). It started Overcharging the battery ontop of everything. Went from 13.5V to 16.8V - Duralast crap. We got a refund and purchased a advanced autoparts reman alternator. The new Alternator is putting out 14.7@ the alternator and 14.5@ the battery. I used my Load tester and tested the battery. Its hold a charge better then most batteries ive seen.

Im going to use the method you described to test the starter but I know the starter is a issue in more then one way. Wont spin fast enough to keep the starter gear on the flywheel and sluggish starts at full voltage on the battery.


on a side note between those 4 Alternators i found a few issues.

alot of corrosin on the Alternator wire and internal breaks - Remade a wire for the alternator

Connection to the battery from the power cable was snug not tight. - Added a washer to the Terminal.

Fuel Pressure Regulator is going bad making it hard to start.

The first 2 issues might haved killed the original alternator but all the Duralast crap Alternators died on thier own accord.

 

Never ever buy cheap auto parts store electrical items. Specifically fuel pumps, alternators, starters, O2s, compressors, motors of nearly every kind and probably a few I can't think of.

Buy only quality names if you AREN'T going to buy OEM. Dura-anything is garbage regardless of how many times you see a commercial for it.

 

I had so much trouble with some of the same things - bad positive cable and then ground(s). When done it charges very well and the new Optima stays up for weeks at a time.

The bad + cable took out the new 140A Powermaster alternator quickly. Then the bad grounds caused erratic charging.

 

if you car isn't idling correctly the alternator isn't going to be putting out enough to maintain the battery. i was having this problem till i tuned my idle properly. the battery would constantly need a jump. it could also be a combination of a bad/burnt heat sink or wire or a connection issue.