S2000 Under The Hood S2000 Technical and Mechanical discussions.

Bad alternator?

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Old Aug 3, 2008 | 02:00 PM
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Default Bad alternator?

So after doing some searching and compiling some information I decided to post my recent problem.

It started the other day when I was leaving work. I jumped in the car to leave and went to start it, but it would not start. The starter ticked a few times and then quit, all my lights in the dash got super dim, almost to the point you could not see them. I let it sit after a minute the dummy lights in the cluster lit normal again but my fuel, temp, speedo and tachometer were still really dim. I tried to turn it over again and the same thing happened. I asked one of my buddies if he would give me a jump, we jumped the car and it struggled to start for a few seconds and then it started. I let it warm up and it seemed to be running fine so I headed home. On my way home I approached a red light, as I depressed the clutch and put the car in neutral the car almost died, it dropped down to the last LED on my tach so I gave it a little gas to keep it from dying. Needless to say this happened several times during my 25 mile trip home. Once I got home I turned off the car and tried to restart it. Unfortunately it would not start. A few hours later I jumped my car at my house and put a voltmeter on the battery as the car was running, it said I was putting out 14.6 at the battery. Sounds normal to me. I went in the the cabin and noticed that my battery light was on, if I recall correctly, your battery light comes on when your charging system has stopped charging the battery.

I have already pulled the alternator and checked the brushes, they looked good, I also had a extra regulator laying around so I replaced it. I put the starter back in and all the symptoms are still present. I have checked my fuse and all the connections I could trace. My next move is to take the alternator back out and have it tested at the stealership or Checkers.

I was wondering if it is possible my alternator is putting out AC current some how, and/or if there could be a short in the stator.
?
Any help and past experiences would be greatly appreciated. Thanks in advance..

V
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Old Aug 3, 2008 | 03:31 PM
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I don't mean to suggest the obvious, but did you check the no-load voltage on the battery? Anything under 12.8 with the engine off is a bad battery.

I suspect that the battery has failed catastrophically inside and is pulling down the electrical system. At the very minimum, I'd start by swapping in a new battery. If the charging system is putting out 14.6 at idle, I sincerely doubt there's anything wrong with it.

Mike
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Old Aug 3, 2008 | 04:16 PM
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Yeah I checked the battery a few times, the first time I checked it was after I got home from work, it read 12. something and then after trying to start it, it read 8. something. I was under the impression anything over 9.6v was good anything below was bad. I thought it possibly could be my battery, but it is pretty new so I have over looked the possibility. I will considder replacing the battery tomorrow. I figured that I had a low charge on it because of the alternator. Could a bad battery cause my car to almost die at idle?
Thanks for the suggestion I'll look into it a little more.
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Old Aug 3, 2008 | 05:27 PM
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You have to remember that today's alternators are not designed to recharge a completely dead battery. It is always advisable to start off with a fully charged and functioning battery. If your battery has had a bad cell for a while, for example, the alternator is already working overtime trying to charge it. As suggested, get a new batt and do a complete charging system test. Good luck
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Old Aug 3, 2008 | 05:44 PM
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Do you think I could pull my battery and throw a slow charge on it until it is charged, or would you suggest compleatly replacing it.
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Old Aug 3, 2008 | 10:47 PM
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It depends on age. If the battery is close to being 5 years old, I suggest you replace it. You can try a slow charge try again if the battery is rather recent. Voltage needs to be at least 12.66v. After that you can get a "VAT" test performed at most automotive shops where they check the battery CCA, charging system and ALT output. This way they can narrow down the source of your problem. Not sure if Autozone does this for you
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Old Aug 3, 2008 | 11:51 PM
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battry, replace it, no harm , no foul
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Old Aug 4, 2008 | 08:43 AM
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Ya freakin' cheap bastid. Just buy a new battery already.
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Old Aug 4, 2008 | 10:19 AM
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Originally Posted by SheDrivesIt,Aug 4 2008, 08:43 AM
Ya freakin' cheap bastid. Just buy a new battery already.

I think I am going to pick up one after work.

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Old Aug 5, 2008 | 08:01 PM
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Good news and bad news. I replaced the battery and the car started good, but.... the battery light is still on. I tested the battery under load and got 14.40, so I know I am getting voltage from the alternator. I pulled the alternator back out and will take it to the auto store tomorrow and have them test it.



BTW: I appreciate all your guys input, I hope we can figure this out soon without having to go to the dealership...
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