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Old 03-05-2018, 05:03 PM   #1
70zz4
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alt wireing

hi guys ' iam switching my 1970 c10 to a serpentine system;wondering what changes need to be made to the electrical. Also do i delete the regulator?ect. thanks
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Old 03-06-2018, 04:12 PM   #2
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Re: alt wireing

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Originally Posted by 70zz4 View Post
hi guys ' iam switching my 1970 c10 to a serpentine system;wondering what changes need to be made to the electrical. Also do i delete the regulator?ect. thanks
If your charging system is working OK all you have to do is change the front pulley on the alternator to a serpentine pulley, but be sure the diameter is the same as stock.

I always recommend ditching the old externally regulated alternator and voltage regulator for a more modern style, SI or CS, but if you're happy with it then just change the pulley. The conversion is very easy to do so don't be afraid to try it if you decide to go that way.
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Old 03-11-2018, 10:15 AM   #3
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Re: alt wireing

thanks for the reply ,can you explain the process of getting rid of the external regulator? Thanks
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Old 03-11-2018, 03:57 PM   #4
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Re: alt wireing

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thanks for the reply ,can you explain the process of getting rid of the external regulator? Thanks
It is quite simple, but first you have to decide whether to use the SI or the CS alternator. The SI alternator was used up until the late eighties and then GM went to the CS series.

If you use the SI alternator you will need to locate the brown wire on the end of the external regulator plug. You will need to extend it to the no.1 terminal on the SI alternator. Then you need to locate the red wire on the external regulator plug and extend it to the no.2 terminal on the SI alternator. Then just reconnect the large output wire to the back of the SI alternator.

Here is a picture with instructions.

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The other two wires on the external regulator, the white and the blue one can be used to extend the brown and red wires or they can be removed from the harness.

One way to use the blue and white wires is to jump them in the plug like this.

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the plugs on the alternators are different so you will need to adapt the wires to the SI alternator. The easy way to do this is to purchase the SI plug at any auto parts store for about $5.00 and splice the wires or get new terminal ends for the adapter and crimp them onto the brown and red wire extensions.

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If you happen to have the alternator for the engine with the serpentine system and it is working OK, you can bolt it on and wire it to the same brown wire from the external regulator to the L terminal on the CS alternator. The red wire will extend to the S terminal on the CS alternator.

Some of the later years only use the brown wire in the alternator plug. I think it's after 1996.

The only thing that has to be done different is to solder a resistor inline with the brown wire before it gets plugged in to the CS alternator L terminal. This is done to protect the diodes inside the alternator internal regulator.

You can buy an adapter plug from the auto parts stores with the resistor installed and the right plugs to go from the old stock alternator to the new CS style for about $ 30.00 but if you have the CS harness you can just splice in the brown and red wire to the CS harness wires that connect to the L and S terminals. Just be sure to solder in a resistor in the brown wire. the resistor value can be anywhere from 85 ohm 5 watt to 300 ohm 1 watt to protect the regulator in the CS alternator.

Here is an adapter to go from the SI alternator to the CS and yours would have the older 10 DN plug on one end.

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You can find these stock CS harnesses in any junkyard to plug into the CS alternators.

Any questions just post them up.
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Old 03-11-2018, 04:14 PM   #5
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Re: alt wireing

Here is a thread that explains a lot more about the conversion just don't let it confuse you because it is very detailed about how the charging system works.



http://67-72chevytrucks.com/vboard/s...d.php?t=417872


One thing that makes a difference is whether you have the gauge dash or the idiot light dash.

If you have the gauge dash you have to wire the output wire to the stock location or the battery gauge will not work. the thread above explains it.
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Old 03-11-2018, 06:38 PM   #6
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Smile Re: alt wireing

wow thanks alot i have a very busy week coming up, but will definitely try to study this info. Again much appreciated!
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Old 03-20-2018, 08:15 PM   #7
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Re: alt wireing

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Originally Posted by VetteVet View Post
Here is a thread that explains a lot more about the conversion just don't let it confuse you because it is very detailed about how the charging system works.



http://67-72chevytrucks.com/vboard/s...d.php?t=417872


One thing that makes a difference is whether you have the gauge dash or the idiot light dash.

If you have the gauge dash you have to wire the output wire to the stock location or the battery gauge will not work. the thread above explains it.

My current set up is stock external regulator on 70C10 w/ gage dash.
I want to use serpentine alternator from 97 GM motor.

I read through the material and still very confused.
Was planning to use the adapter to go from SI to CS.

Confused about what output wire your post is describing for the gage dash to work.
Any further info very much appreciated.
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Old 03-21-2018, 01:22 AM   #8
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Re: alt wireing

Quote:
Originally Posted by 70zz4 View Post
My current set up is stock external regulator on 70C10 w/ gage dash.
I want to use serpentine alternator from 97 GM motor.

I read through the material and still very confused.
Was planning to use the adapter to go from SI to CS.

Confused about what output wire your post is describing for the gage dash to work.
Any further info very much appreciated.
Very simple, it's the wire off the back of the alternator that goes to the main junction in the truck harness where the wire from the battery and the wire to the cab and the wire to the voltage regulator are joined.,

You see, the battery gauge tells you whether the alternator is charging or the battery is discharging, by reading the voltage output of each one. It does this by connecting a charging wire between the two, called a SHUNT. Then a small wire from the battery and another one from the alternator connect to the end of the shunt wire, and they each go to a side of the battery gauge.

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The circle with the blue arrow is the main junction and the small wire with the fuse is the alternator side of the battery gauge, up by the battery is the other wire on the junction block that is the battery side of the gauge. It also has the fuse in it to protect the battery gauge from over voltage. If either fuse is blown the gauge will not work.

If you notice, the large red wire from the back of the alternator is routed here and the wire on the left edge of the diagram connects the alternator output wire to the battery positive post via the fender junction and the fusible link from the battery post. that wire is the shunt. If you run the alternator wire straight to the battery or to the starter post, it won't be connected to the end of the shunt and the gauge wire won't be able to read the voltage output from the alternator.

Here is how I convert the OEM system or an SI charging system,to the newer CS alternator. You can see that the wiring is very similar. You just have to run the stock brown wire that went to the external voltage regulator, to the L terminal om the CS alternator, with a resistor soldered inline.
And the red wire from the external regulator plug which also goes to the main junction, to the S terminal on the CS alternator.

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You don't need any adapters if you can find the CS harness with the plug for the alternator. The junkyards are full of them since they were used on about every GM car and truck made after 1986. Once you get the plug in for the alternator all you have to do is splice the brown wire into the the brown wire in the plug harness, don't forget to solder in the resistor, and splice the red wire into the S terminal wire. You won't need any of the SI stuff that is there.

If you can't find the brown wire for the L terminal that went to the original voltage regulator plug, it starts at the firewall block by the master cylinder.

I recommend that you upgrade the alternator output to an 8 gauge wire for the extra amps you may draw with the larger alternator. All the other red wires are 12 gauge from stock and they are large enough

Hope this helps.
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Old 03-22-2018, 09:56 PM   #9
70zz4
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Re: alt wireing

very much appprerciated!! not only good instructions but also the reason why, and how it works
GREAT INFO
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