Bad Alternator?
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Joined: Feb 2012
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From: Brandon MS
Bad Alternator?
Since I've owned my 93 whenever you turn on the blinkers the voltage meter would rock down and up, but the digital voltage readout was always around 14 volts. Driving today the digital voltage reads 12.0 - 12-3 volts with no accessories but the radio on. Turn on the lights and A/C and the digital gauge drops to 11.9. Does this sound like a bad alternator, bad battery, or both. I believe my car has a 124 amp alternator. If I need a new alternator would it hurt anything to put a 140 amp alternator on the car. Everything is stock except that I added a stereo system that has two power amps so I thought the bigger alternator would be ok. Thanks for any advice.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
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From: Orlando FL
Sounds like the voltage regulator in the alternator might be dying. But it sure sounds like the alternator is defective in any case. Putting in a 140 amp would surely not hurt anything and since you have the stereo power amps, it might be best.
I would double check it in any case and check battery voltage with a DVM with engine running. Should have at least 14.0 volts. If it is 12.0 volts or there about, it's not charging. Get the alternator checked.
I would double check it in any case and check battery voltage with a DVM with engine running. Should have at least 14.0 volts. If it is 12.0 volts or there about, it's not charging. Get the alternator checked.
Burning Brakes
Joined: Nov 2010
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From: Crystal Springs MS
Old school check - stick a screwdriver blade to the center back of the alternator (tight fight because the brace is right behind it) with the motor running - if it is magnetized the alternator is charging, or at least trying to. Like Pcolt stated the voltage regulator may be going out, though...and a 140 amp alternator is not a bad idea. Double check your battery connections and grounds, especially after your amp installation.
The 2 power amps...does the alternator whine and/or squeak when you first crank it in the morning, then quiet down? Then it's charging and your amps may be pulling the battery down overnight, causing some of your issues. Ask me how I know this little nugget...
The 2 power amps...does the alternator whine and/or squeak when you first crank it in the morning, then quiet down? Then it's charging and your amps may be pulling the battery down overnight, causing some of your issues. Ask me how I know this little nugget...
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From: Brandon MS
Got battery tested yesterday, tested ok. Got new reman alternator from Napa and installed it. Found that 3 wire connector was broken so replaced that connector plus new ring terminal on wire from alt to battery. Jump started car and it started charging. The sys light flashed a few times by the speedometer. But car was charging fine. Drove car home and it stopped charging on the way home. Put old alternator back on and still no charging. Was hoping is was just bad connector. Going to get new alternator tested this am and hope maybe it is a bad one.
About the sys light, how do you find out what it's trying to tell me. Read that it will flash when you install aftermarket radio but I installed radio in February and yesterday was first time it ever flashed.
I also checked battery cables where they connect to battery and noticed a little corrosion on the positive cable. Will clean it with baking soda and water. The power amp positive is hooked up to power block right behind battery, no corrosion there. The power amp grounds are connected to the frame where the e-brake bolts are mounted. Amps located under seats.
Will post results from testing on new alternator. It is a remanufactured AC Delco 124 amp alternator.
About the sys light, how do you find out what it's trying to tell me. Read that it will flash when you install aftermarket radio but I installed radio in February and yesterday was first time it ever flashed.
I also checked battery cables where they connect to battery and noticed a little corrosion on the positive cable. Will clean it with baking soda and water. The power amp positive is hooked up to power block right behind battery, no corrosion there. The power amp grounds are connected to the frame where the e-brake bolts are mounted. Amps located under seats.
Will post results from testing on new alternator. It is a remanufactured AC Delco 124 amp alternator.
Le Mans Master
Joined: Jan 2006
Posts: 5,621
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From: Orlando FL
Although the SYS indication can mean many things, generally and one of the most common indications of it is a low battery condition. I would go with that for now until you get your charging and battery situation solved properly.
Did you ever get the original alternator tested?
Did you ever get the original alternator tested?
Last edited by pcolt94; Jul 15, 2012 at 01:07 PM.
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From: Brandon MS
Just got the new alternator I bought yesterday tested and it failed. Going back to Napa in the morning and try to get another one. Hope they have another one in stock. When I first installed the new one yesterday I jump started car and the alternator was putting out 13.9 volts according to digital gauge in dash. Let it run a little while, then went home to get my Brother to help get 2 vehicles back home and on the way back the Vette stopped charging. Either I have something that is shorting out the alternator or I just got a bad replacement alternator.
Last edited by black-93-coupe; Jul 15, 2012 at 08:35 PM.
Thread Starter
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From: Brandon MS
I read on another alternator thread that if you put in a new alternator and the battery is real low (like mine was) that the alternator will fry itself because it is designed to maintain a charge, not fully charge a dead battery. Anyone have any thoughts on this?
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From: Anaheim CA
The voltage regulator in the alternator is also a current regulator. It will limit the current that the alternator puts out, which by default protects the alternator from being overloaded by a low battery.
Burning Brakes
Joined: Apr 2012
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From: Ridgecrest Ca
I not only have heard this but I've read this with instructions that come with a new alternator. It's true apparently. I don't know what the actual risk is though but the last alternator I got was for a Ford with an external voltage regulator and the paperwork says to not jump start the car with a very low or zero voltage battery. Always start with a fully charged battery.
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From: Brandon MS
Charged battery last night. Was at Napa when they opened at 8:00 this morning. Picked up 2nd new alternator and went home to replace alternator, reinstall battery, and got it all done and made it to work by 10:00 (on time!!). Car did fine to and from work, about 12 miles each way. Ran at 14.3 - 14.0 volts at startup. Down to 13.7-13.9 after car warmed up. Down to 13.0-13.3 at idle after warmup. So far so good. Thanks for everyone's input and advice. As usual this forum is the best place to learn about these cars we all love. After driving a pick-up on Sunday and a Hummer H3 yesterday, it felt great to drive the Vette today. Although it was fun driving the Hummer yesterday. Felt like I could run over just about anything that got in my way.
Burning Brakes
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From: Morgan Hill and Marina California
leaving the lights on.
Melting Slicks
Joined: Jul 2005
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As far as a dead battery putting too much "load" on an alternator - that's just silly. Think about it - normal power use on your car is in the range of 10 - 30 Amps powering EFI, Ignition, Lights etc. etc. etc. When you have blower on, and defogger on - add another 30 Amps. Even if the alternator was putting another 30 Amps into the battery - it still wouldn't be at it's rated capacity. (Most high output battery chargers go a lot higher than 14.5 Volts in order to fast charge the battery - that's why the fast charge settings are not recommended.)
BUT - if a battery is stone dead (think lights left on overnight) - it can take a while for it to start accepting a charge. If you jump the car, and then disconnect the booster cables - all of a sudden it's like the battery isn't even hooked up. That is a NO NO. Better procedure is to hook up the booster cables with the donor car running - meaning that the alternator in the running car is actually starting to charge the dead battery. Normally after a few minutes - the dead battery will start accepting a charge and then once the car is jump started - the battery will start to charge normally.
Now - if the battery has a shorted cell - that's a completely different story, and that CAN hurt an alternator !!!
BUT - if a battery is stone dead (think lights left on overnight) - it can take a while for it to start accepting a charge. If you jump the car, and then disconnect the booster cables - all of a sudden it's like the battery isn't even hooked up. That is a NO NO. Better procedure is to hook up the booster cables with the donor car running - meaning that the alternator in the running car is actually starting to charge the dead battery. Normally after a few minutes - the dead battery will start accepting a charge and then once the car is jump started - the battery will start to charge normally.
Now - if the battery has a shorted cell - that's a completely different story, and that CAN hurt an alternator !!!