Do I have a GM 'one-wire' alternator? - Hot Rod Forum : Hotrodders Bulletin Board
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Old 04-04-2003, 12:03 AM
Limey Simon's Avatar
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Post Do I have a GM 'one-wire' alternator?

Guys
Being unfamiliar with American hardware, can someone tell me if my GM alternator is a 'one-wire' model, and if so, does it just need the big red terminal connected to the battery-feed lug on the starter motor?

My alternator is a chromed, remanufactured GM item # 7127C from 'Premium Quality AS 500 series' which came in a blue & yellow box. It has a large red bolt-terminal on the back but also the twin spade terminals which could take the 2-wire plastic plug. Do I need to connect the 2 wire plug?

Many than thanks, Limey

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Old 04-04-2003, 05:03 AM
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Normally when an alternator is converted to one wire operation a plug is installed in the place of the dual spade connectors. Other than taking it to the automotive electrical shop I now of no other way to check it out.
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Old 04-04-2003, 07:22 AM
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I was told it was a 1-wire, but how do you tell?If it isn't a 'one-wire' anybody know what to do with the other 2 terminals?

Thanks, Limey
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Old 04-04-2003, 09:38 AM
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There are a lot of sites I've found on Google that pertain to GM alt and conversion. I installed a GM alt like yours on my Commando. I found my info on a Jeep site, but found a lot of other info on them on the web.
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Old 04-04-2003, 09:38 AM
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You can verify it's a one-wire by opening up the case and looking for the letters "SE" on the voltage regulator. If it's already installed on the vehicle you have to polarize it the first time to get it to work. You just use a jumper wire to supply current to #1 or #2 connector on the side. It won't hurt anything touching either post. If it's a true one wire it should start charging after you have the engine rev some where around 1200-1500 rpm's. If it doesn't charge then it's not a one-wire. You will then have to connect a wire from the key on "ignition" source to terminal #1 and make a short jumper wire from the big terminal on the alternator to the #2 terminal and your done.

Joe
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Old 04-04-2003, 08:12 PM
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you can verify if it's a one wire by hooking it up to yer freakin battery and seein if it charges. duh <img src="graemlins/crash.gif" border="0" alt="[crash]" />
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Old 04-05-2003, 10:00 AM
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Sounds like it isn't a 1 wire if you can see the spade terminals. Bullheimer is right with connect the Big + terminal to main wire Bat + at the starter or main + junction and see if it charges if not then you need another wire with key on power to go to the S or + spade. The other terminal goes to the alternator light curcuit to turn off the alt. dash lightif equipped.It's a ground for the light when no charge is there and power when it's charging.
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Old 04-07-2003, 01:31 AM
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Thanks for the advice guys. I'm in final stages of my rod build up but I can't run the engine for the 1st time until I've done the wiring (chicken & egg!). Took it to an electrical store & its not a one-wire after all, so you guys were all right. I'll wire in the extra connections
Cheers, Limey
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