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

Alternator help needed

  • Thread starter Thread starter 2003 Mustang Girl
  • Start date Start date Mar 25, 2018
2

2003 Mustang Girl

New Member
Mar 25, 2018
1
0
1
Mar 25, 2018
#1
  • Mar 25, 2018
  • #1
Hi all,

I need help.

Over the last 10 months we have put 3 alternators and one alternator harness on my 2004 4.6L with 128K miles

The first two and the harness went away under normal driving conditions last May. The battery light came on, the car shook and shuddered before stalling. We were always able to restart the car.

The third alternator came after drag racing the car in January. The battery light came on. No shake or shudder, car didn't die. We replaced the alternator right away. Raced the next day with no issues.

I made 4 passed yesterday then put the car away for the day. The most recent issue was today. On my fourth pass today, at about 300 feet out the gauges started going crazy, then I noticed the car wasn't shifting properly, auto trans was left in drive. By the end of the pass the call fell off by half a second. By the time I got back to my pit the car was shaking and shuddering, gauges going crazy and then finally died. It would not start. Battery appears to be fried as does the alternator.

Any thoughts? Anyone know of a good, solid alternator that will stand up to racing? Stock ones do not.
 

wmburns

SN Certified Technician
Aug 14, 2009
5,892
514
204
Houston Texas
Mar 26, 2018
#2
  • Mar 26, 2018
  • #2
My thoughts are that you are over speeding the alternator. This is causing the alternator brushes bounce and loose connectivity at the slip rings and drop off.

Instead of trying to find a more sturdy alternator why not switch to a larger alternator pulley or a smaller crank pulley.

Another option is to switch to an alternator pulley with a clutch (like a sprag). Many later model year cars use these kinds of pulley to prevent "surging" that occurs when large power/RPM swings happen.
 

Neuron

5 Year Member
Nov 6, 2016
859
192
93
Mar 27, 2018
#3
  • Mar 27, 2018
  • #3
Is it new or rebuilt? Is the alternator the same one each time ie all same model from Autozone? Why the harness replacement?
 
You must log in or register to reply here.

Similar threads

Alternator not charging
  • SchwarzStock
  • Jul 6, 2026
  • 1965 - 1973 Classic Mustangs -General/Talk-
Replies
2
Views
71
1965 - 1973 Classic Mustangs -General/Talk- Sunday at 9:21 AM
SchwarzStock
E
2007 GT Stalls when lights or a/c turned on
  • ejscarfo
  • Jun 22, 2026
  • 2005 - 2009 Specific Tech
Replies
2
Views
129
2005 - 2009 Specific Tech Jun 29, 2026
ejscarfo
E
A
Resolved Electrical Help Please
  • Alabama
  • Jan 22, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
2
Views
278
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Jan 22, 2026
AeroCoupe
F
Alternator Not Charging
  • Fri Guy
  • Aug 29, 2025
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
7
Views
421
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Aug 31, 2025
AeroCoupe
B
Cant Figure Out P0340 Issue
  • Blackout67
  • May 31, 2025
  • SN95 V6 Mustang Tech
Replies
5
Views
399
SN95 V6 Mustang Tech Jun 8, 2025
Blackout67
B
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?