Battery Light Turns Off And On

Alez

New Member
Mar 9, 2016
5
0
1
25
Phoenix, Az
First time poster on here and this is my first car. I bought my Mustang under the impression that everything ran fine, was not the case. So I have had to put in quite a bit of money on my car. One of the problems I have noticed is that the battery light turns on and off from time to time. The car has never turned off though, it has been doing that for about three weeks now. I took it to Autozone and got the battery and alternator checked, both of them were said to be fine. I checked the fuse (I think that is what it is called) and that is fine. What I am thinking is the alternator passed the test because I had just turned on the car. I read somewhere that happens but when the car "heats up" that is when the battery light turns on. The light only turns on with about 30 minutes of driving in it. What do you guys think?
 
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Gearbanger 101

Straight Outta Locash
Super Mod
Aug 10, 2002
9,457
1,375
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Ontario, Canada
Your problem is a worn brass slip rings on the rotor assembly. After some miles, the brushes tend to wear a grooves in the slip rings, which causes them to make sporadic contact with one and other. This is why the charge light tends to go on and off intermittently. Very common.

How they're supposed to look....

64-37077.jpg


How they look like when worn....

2003_Audi_B6_A4_3_0_Bosch_150A_alternator_slip_rings_137000_miles.JPG


You can sometimes do it on the cheap if you can set your rotor up in a lathe and sand/machine down the high spots so the surface area is smooth again. Of course, that will all depend on how deeply the grooves are worn. Otherwise, you're in need of a rebuild my friend.
 

Alez

New Member
Mar 9, 2016
5
0
1
25
Phoenix, Az
tell us more about the car, year etc
Sorry for replying so late I didn't think anyone would reply back, thanks. It is a 2005 V6 Mustang, just a mustang not a gt. It is at 101,000 miles with 210 HP. I'm not really a car guy so I don't really know anymore details, sorry. With that being said I did have to get the transmission rebuilt due the third gear being completely gone (yeah I know stupid right?) I doubt that has anything to do with it though. My brother will be checking the ground cables (I think that is what they are called) to see if any of them are loose or shorted out. Please and thank you for any help
 

Alez

New Member
Mar 9, 2016
5
0
1
25
Phoenix, Az
Your problem is a worn brass slip rings on the rotor assembly. After some miles, the brushes tend to wear a grooves in the slip rings, which causes them to make sporadic contact with one and other. This is why the charge light tends to go on and off intermittently. Very common.

How they're supposed to look....

64-37077.jpg


How they look like when worn....

2003_Audi_B6_A4_3_0_Bosch_150A_alternator_slip_rings_137000_miles.JPG


You can sometimes do it on the cheap if you can set your rotor up in a lathe and sand/machine down the high spots so the surface area is smooth again. Of course, that will all depend on how deeply the grooves are worn. Otherwise, you're in need of a rebuild my friend.
Sorry for replying so late. I am noticing that the battery light is start to become more common. Okay if that is the problem which I'm hoping is a simple swap out or something. How much would I be looking at for a new one? Would I be able to do it myself? Or would I have to take it to a shop for that specific issue? Please and thank you for your help