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Old 04-01-2018, 11:27 PM   #1
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Join Date: Dec 2013
Location: Lampasas, Texas
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LS swap wiring help

Needing help with these 4 wires
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Old 04-08-2018, 05:26 PM   #2
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Re: LS swap wiring help

Originally Posted by jdalexa84 View Post
Needing help with these 4 wires
You can bypass the PCM neutral start and just run the stock factory wiring. The circuit is easy as shown below.
The starter solenoid is a purple 12 gauge wire from the key switch to the neutral start switch on the steering column then through the firewall to the starter solenoid.

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You can do the same thing with the alternator wire by running a wire from the key switch accessory terminal with an 85 ohm 5 watt resistor inline to the L terminal on the alternator. Look on your key switch plug and see if there is a smaller brown wire with a white or yellow stripe that runs to the inside of the firewall plug behind the fuse panel.
This is the alternator exciter wire for the stock harness and it comes out on the engine side of the firewall block as a solid brown 16 gauge wire that originally went to the external voltage regulator. Then a white wire from the regulator went to the alternator.

I put the resistor in the brown wire and run it to the L terminal on the CS alternator. Looking at this diagram you can make the alternator work just fine. You won't need the PCM for charging.

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If the alternator has an internal voltage sensing capability for voltage sensing you won't need to run a wire from the main junction to the S terminal. I believe the 95 and later models used the PCM for that. You should still be able to connect the L and S terminals with an older plug from an earlier harness. I don't have a schematic that shows the connector and the terminals that you refer to. The brown wire is the alternator exciter wire to start the alternator charging so you definitely need that. The resistor can be anywhere from 85 ohm to 300 ohm 1 watt. Or you can get a one-wire alternator.

That's the best I can do for now.

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Last edited by VetteVet; 04-08-2018 at 06:10 PM.
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