Alternator: 3-wire or 4-wire?
Thread Starter
Melting Slicks
Joined: Aug 2005
Posts: 2,606
Likes: 5
Alternator: 3-wire or 4-wire?
I know there are 1-wire alternators and 3-wire alternators, but...I looked at mine closely tonite in anticipation of upgrading and noticed 4 WIRES!
2 - small wires to the plastic plug coming from the top of the alternator (internal regulator?).
1 - large red wire to the single pole on the back of the alternator.
-and-
1 - large ground wire.
Total: 4 wires.
So...I have a 3-wire alternator, right? (Car is '74 SB)...
2 - small wires to the plastic plug coming from the top of the alternator (internal regulator?).
1 - large red wire to the single pole on the back of the alternator.
-and-
1 - large ground wire.
Total: 4 wires.
So...I have a 3-wire alternator, right? (Car is '74 SB)...
Racer
Joined: Apr 2005
Posts: 339
Likes: 1
From: San Diego CA
The big red one is the alternator's positive voltage output.
The big black one is the ground wire.
The two in the plastic connector are the field current and the sensing voltage wires (can't recall which is which without my wiring diagram).
The sensing voltage wire detects voltage changes in the car's electrical system. When changes occur, the other wire supplies or removes current to or from the alternator to increase the magnetic field which produces more or less voltage output to the system.
The big black one is the ground wire.
The two in the plastic connector are the field current and the sensing voltage wires (can't recall which is which without my wiring diagram).
The sensing voltage wire detects voltage changes in the car's electrical system. When changes occur, the other wire supplies or removes current to or from the alternator to increase the magnetic field which produces more or less voltage output to the system.
Thread Starter
Melting Slicks
Joined: Aug 2005
Posts: 2,606
Likes: 5
Originally Posted by big632
Just put a 1 wire on it and make life easier. 
http://www.madelectrical.com/electri...hreewire.shtml
Le Mans Master
Joined: Jan 2001
Posts: 6,938
Likes: 1
From: San Diego CA
Originally Posted by TonySinclair
I know there are 1-wire alternators and 3-wire alternators, but...I looked at mine closely tonite in anticipation of upgrading and noticed 4 WIRES!
2 - small wires to the plastic plug coming from the top of the alternator (internal regulator?).
1 - large red wire to the single pole on the back of the alternator.
-and-
1 - large ground wire.
Total: 4 wires.
So...I have a 3-wire alternator, right? (Car is '74 SB)...
2 - small wires to the plastic plug coming from the top of the alternator (internal regulator?).
1 - large red wire to the single pole on the back of the alternator.
-and-
1 - large ground wire.
Total: 4 wires.
So...I have a 3-wire alternator, right? (Car is '74 SB)...
Thread Starter
Melting Slicks
Joined: Aug 2005
Posts: 2,606
Likes: 5
Originally Posted by Cali,68,L-79
Sounds exactly what i have...external regulated. Is there a black square looking relay on the driver's inner fenderwell next to the vacuum tank?
I believe the regulator is built-in (internal)...
Safety Car
Joined: Jul 2001
Posts: 3,921
Likes: 2
From: York PA
You have a 3 wire alternator. The big ground wire is not really needed, but provides a better ground. If you look closley it attaches to the case of the alternator. The case is already grounded through the mounts. Since you already have the wire for a 3 wire get a 3 wire, the sensing wire allows them to work better when the engine is at or near idle. 
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Thread Starter
Melting Slicks
Joined: Aug 2005
Posts: 2,606
Likes: 5
Originally Posted by stickboy
You have a 3 wire alternator. The big ground wire is not really needed, but provides a better ground. If you look closley it attaches to the case of the alternator.
Thanks, all.
Burning Brakes
Joined: Feb 2004
Posts: 958
Likes: 0
From: shawnee ks
Originally Posted by TonySinclair
Race Director
Joined: Feb 1999
Posts: 16,978
Likes: 7
From: In Dreams There Is Truth Ohio
Originally Posted by TonySinclair
I believe the regulator is built-in (internal)...
Starting with the 69 model year, the regulators were built in the alternator
