My alternator went out last year in November. I swapped it out, but the new one was bad. Got a new one and replaced it. Replacement worked and the swapped alternator tested bad at the shop. Seemed like they gave me a bad one. Everything was working fine until last week. I got the battery and brake light on the dash again which what was happening the last time the alternator went out. Autozone tested the alternator as bad. Rec'd a new one, swapped them, and returned the bad one. It tested bad, of course. It worked fine until today. I got the battery and brake light on the dash again. This time it's weird because the battery and brake light are flickering off and on. I rev high, the light stays on. Once the engine returns to about idle, the light starts flickering off. Help!?
I do believe you guys found the problem. Good work!!
Nothing beats being there to look at it.
You have probably been getting 'rebuilt' units which is not bad in itself but if the rebuilder received a batch of bad diodes they may have these failures until they are exhausted.
But, buddy, you ain't broke my record yet; a lousy Saturn (LAST GM I will own!) bought new, ate SIX (6) alternators in 57,600 miles. That wasn't the worst problem; it ate the auto tranny at 31,000 and dropped a rod cap at the above final mileage.
The voltage regulator is best checked with the engine running and a multimeter in hand but a regulator that has failed will fry a battery since the alternators can supply ~17-18 volts.Â
You can buy a usable meter at Radio Shack or Autozone too, for under $20 US complete with Chinglish instructions to decipher.
They aren't single use devices and are good to have around for a lot of household checks too.
With a 'normal' condition assumed, you should see a terminal voltage at the battery of more than 13 volts and less than 14.7 - this latter would not be healthy for very long and a voltage of around 13.7-14.3 volts would be fine.
Turning off the engine, the battery voltage should fall quickly (this is called a 'surface charge') to a value of 12.6 - 12.8 volts and every healthy battery I've owned settled at a very predictable 12.64- 12.65 volts.
If a charged battery continues to drift downward from 12.6, you have some device drawing current beyond that of the electronics in the vehicle.
The cheap meters I mentioned with rare exception will have an 'Unfused' 10 Ampere range accessible by pluggin the + lead into a neighboring jack.
Take the negative battery clamp off and put the black (negative) lead on the battery post, tap the red one on the free clamp to see if it will exceed the 10 Amp capacity of the meter. This won't hurt hardly any meter but a sustained 15 amps surely would.
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PS! It could be kind if you would post back your findings once you have some to help others.Â
Thanks-
For  scspriggs : The last alternator is still in the car and the problems are now my youngest son's. If you are familiar with the '95 SL2, the alternator is crammed down where it cannot breath and with its rating of 125 Amps, this means the poor thing has to dissapate up  to 1250 watts of power with essentially no cooling. It's way too small for that capacity; about the size of the 30 amp unit in an old Chevy Luv.   Â
He wanted the piece of junk with brand new Pirelli tires so I 'sold' to him for $1.
They are supposed to be dropping in an engine this week; I never bothered to drop the pan to get the chunks out.Â
I only mentioned a few of the bigger problems I had with that evil car, I was always replacing something on it and it had an easier life than any car I previously owned.
If I had financed it, I would have stopped making payments and let them repossess the ******* thing since it was 'possessed' all the time I drove it.Â
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Having worked for an Isuzu dealer I have seen this a lot with aftermarket alternators from places like auto-zone, napa etc. For some reason they will do strange things in these vehicles. The fix was to get a Isuzu alternator. We did have good luck with Beck Arnly alternators also. We also had a local rebuilder repair some with good luck too. If all else fails get a used one.
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I just connected my batter charger which also "checks" the alternator, whatever that means. I turn the car on, the battery light is flickering off/on. I connect the battery charger/tester, and it shows the alternator at 92%. Then it will go down to 32, then to 52, then back up to 92 for a bit.
Clarification: I'm not sure how to clarify this except to say that I've gone through my original alternator and three replacements so far. They are refurbished alternators from Autozone. I had them test this alternator right out of the box, and it tested good. Every alternator I've returned has tested bad so either I'm having the worst string of bad luck, or my truck is burning through these alternators via a short or something else. Could it be my voltage regulator? I don't even know how to check that. I hope this helps. Thanks for responding so quickly, Guys!
Ben
FYI - My battery was fully charged when I ran the new alternator
What type of clarification are you looking for? I'm not sure how else to explain it. I'm not technically inclined when it comes to automotive stuff. Let me know. Thanks, again, scs.
Thanks for explaining the clarification request thingy. I did test the battery with my battery charger/tester, and it did test at 12.3 or higher.
You're not making a pest of yourself. I'm an idiot when it comes to this type of thing. I wouldn't have known you needed a fully charged battery if my buddy hadn't been there to help me replace the alternator. So you're asking the right questions for sure.
Thanks for the testing instructions, freetek, and I will most certainly post the resolution. I have a buddy heading over in a few. I've sent him a link to this post. He may comment when we figure this out because he'd be able to explain it better.
Everybody gave me great advice. Lucky for me, my buddies know more about this sh!t than I do. My buddy turned off the lights and had me start the car. He noticed a spark that looked like tungsten in a toaster glowing bright orange for a fraction of a second.
He removed the alt to check the two connections to it. The wire that connects via a nut had some of the insulation torn away. He patched it with electrical tape and put it back together. I told him I'm never gonna be able to do this stuff myself because he does it all for me. Well, I take care of his computer, network, and home theater for him in exchange. The light hasn't flickered since, but we only tested for a bit yesterday. I've got a lot of driving around to do today. I'll let you know if the problem reoccurs today.
Thank you, Guys, for all your help. I haven't really
For freetek:
What a story! You ought to be a comedy writer. Thanks for responding!
Charlie
Clarification on the "request for clarification":
The subject you see in your E-Mail is a standard subject line generated by this system. Until some checks the "solution" box when they respond, the subject will always be "request for clarification". No one has checked the "solution" box yet for fear of giving a not-to-well recieved answer and being penalized with a low rating.
Please forgive me for making a pest of myself. But, how do you know the battery was fully charged? Did you measure the terminal voltage with the battery connected, and did it read 12.3 volts or higher?
FYI: The alternator check the charger is making determines if the alternator output is around 1.5 - 2.0 volts above the battery terminal voltage. If it is in this range, the alternator will test "okay".
Your voltage regulator is probably in the alternator. But, if it's not, you may have a point. You can ask Autozone if there is an outboard voltage regulator.
To freetek:
Did the Saturn finally quit eating alternators, before it reached its final mileage?
Has anyone mentioned that the battery has to be fully charged beofre operating a new alternator. If it isn't the new alternator will be damaged.
Original notice of problem: Battery Light indicator came on with voltage needle indicating battery almost completely dead; Had alternator and Battery tested by care care place, and both came back good..but replaced Alternator anyway. Same problem came up immediately. So got a new Battery to go with that new alternator. Worked good for 2 months..then same problem with Battery light and Battery Indicator. Changed Battery AGAIN.. Two months again..same problem. and all dash lights are also now flickering occasionally. Any ideas?
Original notice of problem: Battery Light indicator came on with voltage needle indicating battery almost completely dead; Had alternator and Battery tested by care care place, and both came back good..but replaced Alternator anyway. Same problem came up immediately. So got a new Battery to go with that new alternator. Worked good for 2 months..then same problem with Battery light and Battery Indicator. Changed Battery AGAIN.. Two months again..same problem. and all dash lights are also now flickering occasionally. Any ideas?
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