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Old 11-16-2020, 10:22 PM   #1
Driver_WT
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Alternator Wiring

I have an alternator from a 1998 S10. Looks like it is a CS130D (according to Rock Auto). At the time I picked up the alternator I also took the alternator connector. It is a four pin connector with only one wire in it (which is in the L position on the connector). When I look up a connector for this alternator on Rock Auto (1998 S10) it shows only one wire.

All of the wiring diagrams I can find for a CS130 alternator show two wires. Do I just use the one wire and do I need a resistor in that one wire (or will the idiot light for charging provide the resistance)?

Thanks.

Wade
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Old 11-17-2020, 04:43 PM   #2
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Re: Alternator Wiring

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/
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Old 11-17-2020, 06:09 PM   #3
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Re: Alternator Wiring

Just to be clear, because I also have the single brown wire on the alternator that's going into my 72 Blazer, together with a new wiring harness: I should put a resistor between the brown wire and the wire that's labeled Alternator Exciter. I think I understand that part.

But you said that for better voltage sensing the output terminal should be wired to the fuse panel and not directly to the battery or starter post. My wiring kit says to run a bypass wire if using an alternator with higher than 80 amp capacity. So if I run a bypass wire, my voltage gauge (which replaced my ammeter) will still read voltage but might not be exactly right. Did I get that right, or am I missing something?

And I realize I'm somewhat hijacking a thread, but I suspect Wade might run into the same type of issue.

Thanks

David
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Old 11-17-2020, 09:44 PM   #4
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Re: Alternator Wiring

Quote:
Originally Posted by VetteVet View Post
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
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Old 11-17-2020, 09:46 PM   #5
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Re: Alternator Wiring

Quote:
Originally Posted by truckster View Post

And I realize I'm somewhat hijacking a thread, but I suspect Wade might run into the same type of issue.

Thanks

David
No worries David. I need all the info that I can get LOL
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Old 11-17-2020, 11:33 PM   #6
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Re: Alternator Wiring

......
Quote:
Originally Posted by truckster View Post
Just to be clear, because I also have the single brown wire on the alternator that's going into my 72 Blazer, together with a new wiring harness: I should put a resistor between the brown wire and the wire that's labeled Alternator Exciter. I think I understand that part.

But you said that for better voltage sensing the output terminal should be wired to the fuse panel and not directly to the battery or starter post. My wiring kit says to run a bypass wire if using an alternator with higher than 80 amp capacity. So if I run a bypass wire, my voltage gauge (which replaced my ammeter) will still read voltage but might not be exactly right. Did I get that right, or am I missing something?

You'll need the resistor in the place you noted.
You should run a larger gauge output wire from the alternator to the main junction usually not the fuse panel. See pic below. I don't think the voltmeter will be affected. You can check it with a voltmeter at the alternator and the battery for comparison.

And I realize I'm somewhat hijacking a thread, but I suspect Wade might run into the same type of issue.

Thanks

David
Quote:
Originally Posted by Driver_WT View Post
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
If you are taking your power feed off the battery cable at the starter solenoid it might be considered a main junction. The best way would be to run the alternator output wire ( 8 gauge ) to the main junction like shown below, however your way will work.It's kinda the same thing.

Notice the sensing wire and the alternator output wire are run to the same spot on the main junction. This one uses a 10 SI alternator so it needs the sensing wire whereas the CS 130 one wire does not. Also the output wire is 4 gauge
which is overkill but this diagram uses a rear mounted battery so maybe they think they need that large of wire.


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This method will not allow the original battery meter AKA ammeter to work so if one needs to have that function the wiring must be different. I would need a different thread to detail that.
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Old 11-18-2020, 07:15 AM   #7
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Re: Alternator Wiring

Got it. Thanks very much. Greatly appreciated.
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Old 11-19-2020, 07:37 AM   #8
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Re: Alternator Wiring

One more question to VetteVet. How do I wire the charging light if I am only using one wire to the alternator?
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Old 11-19-2020, 03:02 PM   #9
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Re: Alternator Wiring

The short answer is you can't. The one wire alternators do not have the internal ability to back feed voltage to the light to allow it to illuminate during charge or discharge. It requires an exciter wire to the L terminal in the alternator.

The gauge dashes can be wired to allow the battery gauge to work with a one-wire alternator if the circuit is wired correctly.
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Old 11-19-2020, 03:55 PM   #10
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Re: Alternator Wiring

Quote:
Originally Posted by VetteVet View Post
The short answer is you can't. The one wire alternators do not have the internal ability to back feed voltage to the light to allow it to illuminate during charge or discharge. It requires an exciter wire to the L terminal in the alternator.

The gauge dashes can be wired to allow the battery gauge to work with a one-wire alternator if the circuit is wired correctly.
Thanks. I was afraid you were going to say that.
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