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Battery light on?

Tiny
ERICLIAM061013
  • MEMBER
  • 2007 FORD MUSTANG
  • 4.6L
  • V6
  • AUTOMATIC
  • 108,000 MILES
I have replaced the battery and alternator and light for the battery came on and the car slowly started dying down.
Wednesday, July 6th, 2016 AT 4:28 PM

22 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Check the fuses and fusible link in picture any of them will effect whether your car charges or not. also recommended replacement of belt and tensioner is 60,000 miles which most of time if bad will not charge at idle or low rpm's. This guide can help us test the alternator

https://www.2carpros.com/articles/how-to-check-a-car-alternator

Check out the diagrams (Below). Please let us know what you find.
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Wednesday, July 6th, 2016 AT 4:52 PM
Tiny
JUSTINLEWIS
  • MEMBER
  • 3 POSTS
  • 2005 FORD MUSTANG
  • 4.0L
  • 6 CYL
  • RWD
  • AUTOMATIC
  • 90,000 MILES
After starting my car, a few minutes later the battery light comes on. The lights don't dim when I'm driving it so I don't think it's the alternator, and everything works fine when I'm driving it as well. I tried cleaning some of the corrosion off (there wasn't very much but I cleaned it anyway) and tightened the bolts to the positive and negative cables, but that didn't fix the problem.
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Monday, October 19th, 2020 AT 1:53 PM (Merged)
Tiny
RIVERMIKERAT
  • MECHANIC
  • 6,110 POSTS
How old is the battery?

Time to get out the trusty multimeter and check battery and alternator output voltage.
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Monday, October 19th, 2020 AT 1:53 PM (Merged)
Tiny
JUSTINLEWIS
  • MEMBER
  • 3 POSTS
The battery is the same one from when I bought the car about a month ago. It looks fairly new, but the guy could have just cleaned it up. I tried looking for a date or any indication of how old it was on the battery itself. Do you know of any way to see how old it is without a voltmeter? I don't have one.
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Monday, October 19th, 2020 AT 1:53 PM (Merged)
Tiny
RIVERMIKERAT
  • MECHANIC
  • 6,110 POSTS
Look for the date code on the side. Alphanumeric.
You can pick up a decent meter at places like Autozone for about 20 bucks. You could also take the car to one of those places and have them do electrical tests, usually for free.
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Monday, October 19th, 2020 AT 1:53 PM (Merged)
Tiny
JUSTINLEWIS
  • MEMBER
  • 3 POSTS
Just checked. The battery is 5 years old, I'm not sure how long car batteries are supposed to last but I'm assuming that's pretty old. I'll run by autozone and have them check it just in case before I buy a new one. Thanks for your help!
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Monday, October 19th, 2020 AT 1:53 PM (Merged)
Tiny
RIVERMIKERAT
  • MECHANIC
  • 6,110 POSTS
My pleasure. Most car batteries last anywhere from 3-5 years. I should rephrase that: Most car batteries have warranties that last 3-5 years.
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Monday, October 19th, 2020 AT 1:53 PM (Merged)
Tiny
JOE PETERSON
  • MEMBER
  • 1 POST
  • 2003 FORD MUSTANG
  • 4.6L
  • V8
  • 2WD
  • MANUAL
  • 122,000 MILES
Battery light goes off and on. Off when I unplug the two wires to the alternator and, on when I plug it back in. I tested both sides of the wires in the harness and get 12.67 volts. I checked wire back to fuse like to fuse box and looks okay. Did not slice open fusible hoping it is okay.
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Monday, October 19th, 2020 AT 1:53 PM (Merged)
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 47,690 POSTS
Hey Joe,

Looks like you need an alternator but to be sure lets follow these guides to replace the alternator and check the wiring.

https://www.2carpros.com/articles/how-to-replace-an-alternator

and

https://www.2carpros.com/articles/how-to-check-wiring

Please run down this guide and report back.

Cheers, Ken
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Monday, October 19th, 2020 AT 1:53 PM (Merged)
Tiny
GEORGIADAWGS2015
  • MEMBER
  • 1 POST
  • 2002 FORD MUSTANG
  • 4.6L
  • V8
  • RWD
  • AUTOMATIC
  • 170,000 MILES
My alternator and battery tests good. What could be the cause for my battery light to flicker during hard acceleration?
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Monday, October 19th, 2020 AT 2:04 PM (Merged)
Tiny
THIS IS MIKE
  • MECHANIC
  • 686 POSTS
Georgiadawgs2015
August 12, 2015.

My 02 mustang gt does not have female spade connector on the alternator. Still trying to find out why my battery light is flickering on and off.
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Monday, October 19th, 2020 AT 2:04 PM (Merged)
Tiny
GEORGIADAWGS2015
  • MEMBER
  • 1 POST
Georgiadawgs2015
August 14, 2015.

My battery and alternator was tested at auto zone.
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Monday, October 19th, 2020 AT 2:04 PM (Merged)
Tiny
THIS IS MIKE
  • MECHANIC
  • 686 POSTS
Georgiadawgs2015
August 17, 2015.

I changed the alternator again. So for battery light not coming on. I've heard mustangs are bad on alternators?
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Monday, October 19th, 2020 AT 2:04 PM (Merged)
Tiny
MICHAELTHEBUS
  • MEMBER
  • 2 POSTS
  • 2001 FORD MUSTANG
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 13,300 MILES
Just in last couple of days, the battery light goes on now and then. Stays on at times 1-2 mins. Or less thank 15 secs. Today it never came on. Can't seem to fix on weather having a/c on effects it. I'm original owner and never had this. Battery is 2006. Living in Phoenix heat never had this effect.
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Monday, October 19th, 2020 AT 2:05 PM (Merged)
Tiny
RACEFAN966
  • MECHANIC
  • 5,029 POSTS
Well I would take it to a local parts store that will do a free charging system test and have them test the system. It may be that the alternator is bad. Also check the battery cable connections for any corrosion is there is corrosion then clean the cables. Let me know what you find. Just for fun any performance mods?
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Monday, October 19th, 2020 AT 2:05 PM (Merged)
Tiny
MICHAELTHEBUS
  • MEMBER
  • 2 POSTS
I read a shortcut. Instead of taking it to a parts store etc. Start the car and then take the " ground " cable off. If the engine dies immediately then the alternator is the problem. Any truth to this?
Thanks Mike.
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Monday, October 19th, 2020 AT 2:05 PM (Merged)
Tiny
RACEFAN966
  • MECHANIC
  • 5,029 POSTS
NO please do not do that. This is only a good test on generators not alternators. This will spike the alternator and could ruen it and maybe even spike the computer and take it out too. SO please NO don't do it just go to the local parts store and have it tested they usually do this for free so the only cost is the gas. Let me know what you find with the test.
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Monday, October 19th, 2020 AT 2:05 PM (Merged)
Tiny
SILVALEX
  • MEMBER
  • 1 POST
  • 1995 FORD MUSTANG
  • V8
  • 2WD
  • MANUAL
  • 110,000 MILES
Hello, I have a 1995 mustang gt that's not charging. I've checked the fuses, replaced the alternator and still nothing. I also don't get the alt light in dash when I turn key on, if my model year has one?
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Monday, October 19th, 2020 AT 2:06 PM (Merged)
Tiny
CARADIODOC
  • MECHANIC
  • 33,874 POSTS
That missing light is a big clue as that provides the turn-on signal. Measure the voltage on the green / red wire in the plug on the back of the generator and holler back.
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Monday, October 19th, 2020 AT 2:06 PM (Merged)
Tiny
BDEPTAWA
  • MEMBER
  • 1 POST
  • FORD MUSTANG
I have a 2000 mustang. It has a V6 3.8 liter engine. It has 128,000 miles on it. The indicator light with a battery on it came on and im not sure whats wrong. I cleaned the posts of corrosion but light still on. I took it to auto zone and had the battery checked and the man said I need to charge the battery. My question is why would I need to charge the battery?The car is running and starting fine-and how do u charge the battery?
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Monday, October 19th, 2020 AT 2:06 PM (Merged)

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