alternator wiring

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awdblazer

Master Mechanic
Dec 12, 2013
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so i have a 3 wire alternator on my cutlass now
but i plan on putting on my 105amp when the ls goes on
the current wiring is heavy red from battery, so that goes to same spot on ls alternator
but what has me stumped is the smaller red and brown?
thanks
 

pagrunt

Geezer
Sep 14, 2014
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The small red is part of the battery circuit (circuit 2) & is spliced into the bigger wire in the harness. The brown is the for the gen/battery light (circuit 25).
 

pontiacgp

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Mar 31, 2006
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the brown wire excites the alternator, without it the alternator won't charge the battery unless you wire the alternator differently. What style of alternator is the 105 amp alternator
 

awdblazer

Master Mechanic
Dec 12, 2013
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its just a stock alternator from a 2004 silverado
so what do i hook up to what on the new alternator?
 

pontiacgp

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Mar 31, 2006
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ls-alt.gif


on the 12 volt (B) switched a 500 ohm, 1/2 watt resistor should be wired between the alternator and the brown wire

or you can buy the conversion harness...

Delco 8078/GM 12102921 if you have a volt gauge or
Delco 8077/GM 12083462 if you have an "idiot" light.

cssiharness.jpg
 
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awdblazer

Master Mechanic
Dec 12, 2013
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so with that do i need a resistor? what is the resistor for? i have a voltmeter in my car
 

drogg1

G-Body Guru
Jan 25, 2009
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I presume the conversion harness has the resistor in that shrink tubing. The brown wire is what initially excites the windings in the alternator so it can begin generating power. The resistor is to limit the current in the windings to about 12 V / 500 ohms = 24 mA. Without it, I imagine the windings will eventually overheat and be damaged. It needs to be 1/2 Watt because (0.024 * 0.024) * 500 = 0.288 Watts.

This diagram:

http://www.maliburacing.com/wiring_diagrams/ChargeCircuit.jpg

shows it to be a smaller resistance but then you need a higher wattage resistor. It probably is not critical so long as there is some current limiting. If you have an voltage idiot light, I think it serves to limit the current instead of the resistor.
 
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pontiacgp

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Mar 31, 2006
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so with that do i need a resistor? what is the resistor for? i have a voltmeter in my car

the resistor takes the place of the small light in the OEM volt gauge, without it the alternator will not charge the battery. I have the conversion wire in my GP and I can verify that it works
 
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pagrunt

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Sep 14, 2014
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Here is what my shop manual covers the operation, this follows the diagram from the link in my manual. I'd scan it but my scanner died.
Circuit Operation: With the Ignition Switch in Start or Run, Battery voltage is applied through the Gage Fuse and the Generator Warning Light to terminal L (brown wire) of the Gernerator on models equipped with warning indicator. The 40 ohm Resistordraws current and the Warning Light glows. Current flows through the Gernerator Field Winding. On models with optional Gages ("A" Series only) initial voltageto the generator is provided through the 10 ohm resistance wire.
The rotatingfield and the rectifier diodes produce a DC output voltageat the BAT terminal. DC voltage ia also appliedto the field winding, through the Diode Trio.
Whenever the generator output voltage is low, the regulator increases the currentin the field winding. This causes the output voltage to increase.
Field current is provided by the Diode Trio or from the Battery through the Generator Warning light.
At low engine speed, current flows from the Battery through the Generator Warning Light to the Field Winding. The Generator Warning Light is lit whenever the Battery supplies field current. As the engine speed increases the Generator output voltage increases and the field current is supplied by the Generator through the Diode Trio. When the voltage on each side of the Generator Warning Light is about the same, the light goes out.
 

pontiacgp

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Mar 31, 2006
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with all due respect a few of you guys are over thinking it....guys before us have already figured it out....:)
 
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