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  • 1996 - 2004 SN95 Mustang -General/Talk-
  • SN95 4.6L Mustang Tech

battery light when rpm's hit 4k

  • Thread starter Thread starter Mystic1350
  • Start date Start date Aug 22, 2011

Mystic1350

Member
Oct 12, 2009
82
0
6
Sandy Hook Area NJ
Aug 22, 2011
#1
  • Aug 22, 2011
  • #1
So i have posted this issue before i.e. right around 3.8k-4k, voltage drops and battery light comes on, flickers, then goes away after that rpm range.
Thought i had fixed problem when i bought a quality PA Performance alternator (after i thought the remanuf one i bought that lasted 6 months prior was no good), however issue is still there.

I have heard that if my problem exists as it does, it could be the voltage regulator on the alternator. I am beginning to think its NOT the regulator and something else with my car that is causing these regulators to short as i couldnt have got 2 badd alternators.

what could be other possiblities non alternator related that could cause this issue on my car?

thanks in advance
 

evolucion311

Member
Mar 19, 2009
236
2
18
Aug 22, 2011
#2
  • Aug 22, 2011
  • #2
The voltage regulator is inside your alternator and is not user servicable. Typically the whole alternator is replaced. The odds are small but maybe you did get a bad 2nd alternator.

Pull yours off and take it to get bench tested at a parts house.
 

Mystic1350

Member
Oct 12, 2009
82
0
6
Sandy Hook Area NJ
Aug 22, 2011
#3
  • Aug 22, 2011
  • #3
i know its in the alternator but is there anything external from the alternator that can cause stress on it causing it to go bad prematurely?
that is my ultimate questions
 

Maxpowers

Member
Sep 9, 2009
859
2
19
Pittsburgh, Pa
Aug 22, 2011
#4
  • Aug 22, 2011
  • #4
The only thing I've ever seen is fluid leaking on to it.

I have changed an alt on a car three times in a week before. All were found faulty.
 
N

n0v8or

10 Year Member
Aug 23, 2003
604
8
39
Rhode Island
Aug 23, 2011
#5
  • Aug 23, 2011
  • #5
If the alternator output voltage briefly becomes too high, the internal regulator will turn on the lamp and shut down the alternator until the voltage drops to a safe value. You could monitor your alternator + terminal with a meter to see if the voltage rises above 16V as you increase engine RPM. Be careful and wear eye protection. If yes, some likely causes are poor battery connections, a damaged wire between alternator and battery, or a battery with a high internal resistance (this condition can be intermittent, and often worse in cold weather).
 
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