• Mustang Forums
  • 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).
 
You must log in or register to reply here.

Similar threads

P
Electrical 2001 GT Overcharging
  • PseudoGT
  • Dec 3, 2025
  • SN95 4.6L Mustang Tech
Replies
1
Views
209
SN95 4.6L Mustang Tech Dec 13, 2025
Noobz347
M
85 mustang 5.0 cranking in run position
  • Mamaclean
  • May 23, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
3
Views
107
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Jun 1, 2026
General karthief
A
Resolved Electrical Help Please
  • Alabama
  • Jan 22, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
2
Views
255
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Jan 22, 2026
AeroCoupe
J
98 GT Alternator will not charge battery.
  • johnsadler05
  • Jul 13, 2024
  • SN95 4.6L Mustang Tech
Replies
4
Views
1K
SN95 4.6L Mustang Tech Aug 10, 2024
johnsadler05
J
K
Engine 2000 Mustang GT - Fuel issue post-blown spark plug repair
  • kenster1092
  • Feb 26, 2026
  • SN95 4.6L Mustang Tech
Replies
4
Views
294
SN95 4.6L Mustang Tech Mar 10, 2026
kenster1092
K
Share:
Bluesky Email Share Link
  • Mustang Forums
  • 1996 - 2004 SN95 Mustang -General/Talk-
  • SN95 4.6L Mustang Tech
Menu
Log in

Register

  • Forums
  • What's new
  • Media
  • Resources
  • Contact
  • Sponsor
X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?

X

Privacy & Transparency

We use cookies and similar technologies for the following purposes:

  • Personalized ads and content
  • Content measurement and audience insights

Do you accept cookies and these technologies?