Four wire Alternator

[JCullen]

I am using a four wire alternator from a 2010 Legacy GT 2.5 turbo on a project car. Can anyone tell me or show me on a diagram which of the four wires are which and what they connect to?

 

[remy6908]

I dont see a four wire alternator connection in the wiring diagrams. Are you sure its for a 2010 Legacy GT?

 

[JCullen]

That is what I ordered. I am building a car using a Subaru Legacy GT 2.5 turbo and need to wire up the alternator before I try to start up the project.
The alternator I received has a three wire plug (pretty standard 3 wire plug) plus the is a larger stud with nut near the 3 wire connector. That stud is insulated from the case as if a wire is to connect to it. I am assuming that goes to the battery positive but I am not familiar with all of the newer charging systems that use an internal regulator.
My engine management is an expensive ECU and Dash so I am concerned about sending a surge voltage to my electronics.
So it appears there are four alternator connections. I will try to attach a photo.

 

[JCullen]

My project car using a 2.5 turbo from a 2010 Subaru Legacy GT

 

[remy6908]

That makes a little more sense. So it is a 3 wire plug with the stud being standalone. The stud is for the battery. The 3 wire plug is for starter, ignition trigger and ground. That thing is awesome by the way. What is it going to be used for?

 

[JCullen]

That makes a little more sense. So it is a 3 wire plug with the stud being standalone. The stud is for the battery. The 3 wire plug is for starter, ignition trigger and ground. That thing is awesome by the way. What is it going to be used for?

I am 75 yr old and have been a car guy since I can remember. It has only been in the last 15 years that I have able to build my dream car. At 16 I commented many times I wanted a car that I could put on like a pair of pants and it would go like a rocket. Muscle cars never wound my watch. I will autocross with it some and make it street legal.
I started with Mazda RX8 subframes, built my own chassis and body. New short block and rebuilt everything else.
I have built, and or restored many VW bugs through the years but two cars I had not done. This pants rocket and a Model A Ford pickup hot rod. I built the Ford in 2017-18 The Ford has Miata subframes, 4 whl disc, rack & pinion etc. Did have a Miata power train but no aero so put in a 2.3 turbo from an 85 T-bird. Fast now. Handles great.
The 71 bug is the last one I did. I gave it to my wife for her 70 th and our 50th.
Thanks for the info. I was thinking the stud was the battery feed but I have about 3K in the electronics and don’t want to fry that.
I never dealt with these alternators that have the internal regulators so I appreciate the help there.
JCullen

 

[JCullen]

Here it is with body panels.

 

[remy6908]

That is awesome. You sir have lived the life most of us dream to live. I have been building a 944 for over 10yrs and hopefully will complete soon. Good luck with your build, I hope its just as much fun to drive as it looks.

 

[JCullen]

That is awesome. You sir have lived the life most of us dream to live. I have been building a 944 for over 10yrs and hopefully will complete soon. Good luck with your build, I hope its just as much fun to drive as it looks.

I love your quote of Samuel Johnson.
There is wisdom in age and in words.