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Old 02-09-2009, 09:48 PM
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hundred's of 3 wire alt posts and still confused

Here is a page showing a GM alternator hookup:

This one states if you hook the wires together it will drain the battery

Here is another page showing just the opposite?

this one states to tie the wires together? but shows opposite lug pattern?

Please someone clarify which which diagram is correct!

I am wiring a simple 3 wire alternator to a race car... nothing fancy.

assuming the wiring is 1 (the bat lug) 2 (closest to the bat lug) and 3 the other lug

I was going to tie 3 into 1 and leave 2 not hooked up or run 2 to an idiot lite.

I guess since 2 goes to an idiot lite it would be switched or can I just run it nowhere? Does it need to be switched?

Someone like DOC please clarify which is correct and what I need to do.

Thanx in advance as always


Last edited by dirtinla; 02-09-2009 at 10:07 PM.
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Old 02-10-2009, 08:07 AM
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I have my three wire alternator hooked up exactly like the second example and it has been that way since the car has been running with no problems. Sometimes the car sits for weeks without me running it and that has not been a problem either.

That picture is a cut and paste from the Painless Wiring web site and I think they know how to wire alternators.

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Old 02-10-2009, 08:10 AM
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The drawing you linked to and posted below is for a Delco S12 internal regulator alternator.

One wire is a jumper from the #2 post on the alternator to the Battery post.

The other wire from the #1 post on the alternator connects to one side of the indicator light (idiot light) and then from the other terminal of the light to the ignition switch terminal that is on only when the ignition is in the on position.

If you do not want to run the charge light, then a diode ( part number is #1N4001 and is available at Radio Shack) can be run in the wire that goes from the #1 post to the ignition switch. This is to prevent "run on" when the ignition switch is turned off.
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