[Driver_WT]

Originally Posted by VetteVet

This is how I think I understand the single wire plug on the cs 130 alternators.
After the 1994 alternators came out GM went to the pcm/ecm controlled engines and
the four and two wire alternator plugs became one wire, usually brown.

The ecm controlled the voltage to the alternator through a charging light via this single wire and they modified the alternator to read system voltage internally between the regulator and the output wire which is connected to the vehicle battery circuits.

The alternator requires a resistance in the brown exciter wire to protect the regulator from over voltage and to prevent feedback current to the ignition circuit which would allow the engine to run on after the key is shut off.

When we install this modern alternator on our old trucks we must use a resister in the exciter wire or we risk burning out the regulator. The charging light is not really enough and I have seen that painless wiring recommends an 82 ohm 5 watt resistor wired between the brown wire and the L terminal on the alternator. I have seen other values from 300 to 500 ohm .5 watt which seemed to work as well.

If you look at the alternator plug-in you may see the 4 pin terminal which the early style alternators had and which had different purposes. They were labeled SFLP or PLIS on the alternator body. The L terminal is the same as your one wire L terminal and the S is for the voltage sensing of the early styles as well. Those two would be the only ones we would use on our trucks. You wouldn't need to use the S terminal but you should use your output wire from the alternator connected to a main junction, rather than running it to the battery positive post or to the starter solenoid, for better voltage sensing.

Here is a link to some of what I am saying.

https://www.chevytalk.org/fusionbb/s...php?tid/74507/

Thank you VetteVet for the very detailed response. Can you enlighten me a bit more on what is considered a "main junction". My current wiring harness diagram says to run the alternator output wire to the large terminal on the starter solenoid and the main feed for my new wiring harness also runs from the large terminal on the starter solenoid to the fuse box.

Wade