Battery Light question - Ford Mustang Forum
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post #1 of 5 (permalink) Old 12-01-2010 Thread Starter
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Battery Light question

My wife has a 2006 mustang v6 4.0, and the other day the battery was unresponsive and car had to be jumped off.
That evening when she got home, I checked the battery(engine off) with multimeter, and found it to be 12.92 volts. Sounds good to me.
I proceeded to start the car and watched the alternator send the volts up to 14.20. Still sounded good to me.
Well the battery light started coming on. I also found corrosion (lots of it) aroung the positive terminal of the battery. I removed the cable clamps and cleaned both clamps and posts with a post cleaning brush.
Still for the next day the light would come on and she explained that the battery light would go on and off as she drove home from work.
The next day, dead battery. We replaced the batter that evening and I figured it must have a bad cell or something.
Were now on the second day with new battery and the light is still coming on. Any ideas?
Could the alternator be going bad? Auto store tested system twice as well. Both tests showed good voltage. One of the tech's said that there was a bad "ripple" in the alternator and it could be going bad. But it's putting out 14+ volts. My wife also explained a whining noise that the frequency goes up and down as the rpm's do. I'm thinking that it could be a bad bearing in the alternator. Wouldn't that impede on the performance at intervals if it has a bad bearing?
Any thoughts,suggestions, any advice would be greatly appreciated!

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post #2 of 5 (permalink) Old 12-01-2010
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Sounds like there's a bad diode(s) in the alternator. That would produce the abnormal ripple and also possibly the battery light.

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post #3 of 5 (permalink) Old 12-01-2010
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usualy when you get a battery light its due to a bad alternator, its not putting out. also a battery can be perfect on volts but what counts also is the amps. take it to a local parts store and they will check both for you free of charge. that way you dont buy something you dont need.

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post #4 of 5 (permalink) Old 12-01-2010
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If it has ripple, it's a bad diode. I'd be replacing the alternator.
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post #5 of 5 (permalink) Old 12-01-2010 Thread Starter
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Thanks for all the help. I will definetly get that replaced!
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