Altenator wires

[txsbuckeye6.2]

I had a friend of mine give me a1985 Cadilac 120amp altenator...I could put it on my 84 k5 6.2 but the plug in the back of the altenator has 3 prongs & the one in my truck only has 2...can anyone help with the wires ...the 2 prong plug on my truck will plug into the caddy alt. but what is the 3rd prong for? The altenator is new & hasn't ever been installed in anything & being that it was free I sure would like to use it ...it does have the threaded stud o
n it to hook up the batt wire also.

Bone it like you own it!
Drive it like you stole it!

 

[kennyw]

Can you post pics? I bet the extra plug will be a tach output...

 

[txsbuckeye6.2]

I wish I could post pics! I'm sittin' here lookin' at it . There are the normal 2 spade terminals & I did try the plug on my truck & it does plug into it,but there is another spade terminal above(toward the front of the alt.) inline with the right side terminal(which I think is #2 terminal on my alt.)

 

[BKinzey]

Can you read any of the numbers on the alt? Maybe find one on eBay that looks the same and post a link here?

 

[txsbuckeye6.2]

no numbers by the spade terminals,2 stickers on it one says ultima 01-0218below that # is 83251759...the other sticker has 830725099 below that # is 20REMANUFACTURED218it is clocked at 12 just like mine..looking down at the top from 12o"clock the 2 normal spades are in the normal place in a blue insulator the other spade is in a white insulator...i'll try to find one on ebay