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

dam alternator wont charge

  • Thread starter Thread starter happydood2
  • Start date Start date Aug 13, 2007

happydood2

Member
Apr 4, 2004
81
0
6
MA
Aug 13, 2007
#1
  • Aug 13, 2007
  • #1
I recently jusyt finished installing my new forged ported cammed pi 2v engine w p51 intake and i finally fired it up today. The problem is my alternator isnt charging the battery. I checked everything. The main wire is bolted up and the plug with the two wires is on. I have a electric water pump that i also wired to one of the two wires on the clip. One wire is constant power and the other goes on with the turn of the key which is the one i connected into. The funny thing is the wires work because without it plugged into the alternator i turn the key and the power goes to the waterpump and on it goes. But when the key is still turned and the waterpump is on i take the clip with the two wires and plug it into the alternator and bam both wires are dead until i shut the car off and unplug it and then turn the key on again. What is my problem here. Do i need a new alternator? I am stumped
 

DTNODYA

Member
Dec 15, 2005
831
1
16
Aug 13, 2007
#2
  • Aug 13, 2007
  • #2
I find your post pretty difficult to follow ... But it sounds like something is hooked up wrong or you alternator is crazy.
 
N

n0v8or

10 Year Member
Aug 23, 2003
604
8
39
Rhode Island
Aug 13, 2007
#3
  • Aug 13, 2007
  • #3
Can you explain what you mean by "the clip"?
Did you re-connect the big braided ground wire from engine block to chassis?
 

happydood2

Member
Apr 4, 2004
81
0
6
MA
Aug 13, 2007
#4
  • Aug 13, 2007
  • #4
the grey plug that goes into the alternator with 2 wires. All grounds are identical when i installed my motor and harness again. I used my girlfriend 04 gt as a map
 
B

BobHyatt

New Member
Aug 7, 2007
378
1
0
Aug 13, 2007
#5
  • Aug 13, 2007
  • #5
happydood2 said:
the grey plug that goes into the alternator with 2 wires. All grounds are identical when i installed my motor and harness again. I used my girlfriend 04 gt as a map
Click to expand...

Your alternator needs the following to charge:

(1) good connection to the + post on the battery and a solid ground;

(2) good battery (not one sitting at 10 volts or something, but a full 12.5+ volts)

(3) a + voltage on that grey connector, so you can't tap into that to run something else, as you will probably lower the current enough that the alternator's regulator will be greatly confused and not charge.

Find another place to hook crap up to, the alternator connections are privileged and need to be left alone when you are thinking about a high-current device like an electric water pump.

That is likely what is keeping you from charging...
 
N

n0v8or

10 Year Member
Aug 23, 2003
604
8
39
Rhode Island
Aug 13, 2007
#6
  • Aug 13, 2007
  • #6
The yellow/white wire to the clip/connector is power to the voltage regulator and is fused with a 20A fuse. If that fuse (marked "ALT") blows, the alternator will not charge. The green/red wire goes to the instrument panel charge bulb, and should not be used for anything else.

Was this alternator transferred from your old engine where it worked OK?
 
You must log in or register to reply here.

Similar threads

J
Power Wire Upgrade Question
  • jhaling
  • Dec 21, 2025
  • SN95 4.6L Mustang Tech
Replies
2
Views
232
SN95 4.6L Mustang Tech Mar 23, 2026
Noobz347
A
Resolved Electrical Help Please
  • Alabama
  • Jan 22, 2026
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
2
Views
259
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Jan 22, 2026
AeroCoupe
Electrical Ron Francis Headlight / Alternator Harness
  • dan50
  • Apr 30, 2026
  • Fox 5.0 Mustang Tech
Replies
0
Views
198
Fox 5.0 Mustang Tech Apr 30, 2026
dan50
Electrical Alternator not charging after terminator 2 install.
  • Sfab79
  • Aug 24, 2025
  • Fox 5.0 Mustang Tech
  • 2
Replies
38
Views
789
Fox 5.0 Mustang Tech Jun 29, 2026
AeroCoupe
F
Alternator Not Charging
  • Fri Guy
  • Aug 29, 2025
  • 1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-
Replies
7
Views
390
1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk- Aug 31, 2025
AeroCoupe
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?