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post #1 of (permalink) Old 06-13-2000, 09:50 PM
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GM alternator, help, glenn

My alternator is crap now that I put a radio in. I can't run more than two electric accessories at the same time (i.e. lights and radio, or lights and turn signal, or fan and radio, or fan and lights.) If I do, something dies on me. So I am going to do the upgrade to the big GM alternator. I just need to know what kind to buy. Glenn's site mentions the year car it can be from, and says a delco 12 si from the auto parts store is the one. But I need a part number. I have found some good prices online, but I don't know if it is the right one. Is it the "single wire" gm alternator? Let me know if you guys have any info. Thanks a lot.


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post #2 of (permalink) Old 06-15-2000, 11:23 PM
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Re: GM alternator, help, glenn

JC Whitney on line 15NV0663Y :12 SI, GM 100 amp alternator
price at about $119.95

Local price is $80 to $120

The Alt. used on the 84/85 is a 12SI. SI stands for
Systems Integral. The was the first GM alt that was
internally regulated. It debuted in 1972.
(That was a 10SI) Of course, GM was the first to come up
with an internally regulated system. This system was an
excellent system. It is so easy to work with and is a
good design. Well, in the 1980s with all of the computer
controlled cars coming out, GM needed an alternator that
could communicate with the ECM. In 1986 the CS series
Alternators came about. CS stands for Charging Systems.
The models, CS121, CS130, CS144 and now CS130D
(this is another story! The number after the CS is the
diameter of the stator in Millimeters. So, on the 86/87
TR it's 144 Millimeters wide. Most all of the CS series
unit put out over 85 amps. The TR Alt. doesn't
communicate with the ECM. Instead, the regulator
monitors everything. It counts the AC counts so it knows
how fast the alt is spinning. and can even cut the
charge back if necessary. There are over 8 different
regulators used in the CS series. They all look and plug
in the same but they are different internally. I could
go on about what each regulator does differently but
that's another time
Upgraded 88 Sam with 100Amp plus Alternator Delco 12SI
used bracket from Rocky Road.
Used local Auto electric shop as alternator source this
is not a stock part buy local save time and money fitted
three alternators before found one needed part number on
unit is useless which sounds about right for a car manufac.

post #3 of (permalink) Old 06-15-2000, 11:32 PM
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Re: GM alternator, help, glenn

How much should I expect to pay for one of these, something around 100amps? I don't want to find out later that I got ripped off? Thanks for the help so far.


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post #4 of (permalink) Old 06-16-2000, 10:58 PM
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Re: GM alternator, help, glenn

I used a single wire remanufactered GM alternator that I picked up at a local shop. Just ask them for a converted hot rod alt with the single wire hook up. You can get the plans to alter the sammy bracket from It is an easy afternoon project if you have a welder or a buddy with a welder. Your idiot light on the dash will no longer work properly and I suggest purchasing a Volt meter to mount somewhere to watch you new alt work.
Good luck.

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