More help please on CS TO SI

[mavtricks71]

If I was to swap my Original SI12 Alternator to my cs130 Alternator in my 1986 k10 there is a pigtail adapter Ac delco PT2145 that could work is this the one i need? My truck has the volt Gauge in the dash .

 

[nvrenuf]

I used the pt2145 to wire my alternator because the original wiring was cobbled up but that pigtail did look like it would be perfect for the conversion.

 

[mavtricks71]

So you did use it on your square body truck? I have read a lot of threads i hope some more people can chime in cause I guess if you have an idiot light you have to run a resistor......my truck has a gauge.

 

[bucket]

So you did use it on your square body truck? I have read a lot of threads i hope some more people can chime in cause I guess if you have an idiot light you have to run a resistor......my truck has a gauge.

I still to this day do not understand why a resistor would be needed. I've installed several of the CS types in place of SI types and not used a resistor. One of them was back '06 or so and it still works to this very day. Millions of CS/gauge equipped GM vehicles were produced, and no resistor that I can find in the factory service manuals I've looked at. I just don't get it.

Unless the factory gauges have enough resistance built into them?

 

[bucket]

Oh, you also don't actually have to use a resistor at all, as a 194 bulb and socket would be the equivalent of an idiot light. The PO of my '77 K5 converted it that way and I just left it. It's actually kind of nifty to have an underhood charge light, lol.

 

[squaredeal91]

I think @82sbshortbed went though this over this last summer?

 

[Catbox]

Some where in my truck's thread we did this as well.
I don't remember what pig tail we used, but it charges like a champ now.

 

[mavtricks71]

So my instructions from GM with the cs130 Alternator " use a 50ohm resistor or charge indicator lamp damage will occur...... But again my truck has a gauge. I havent bought the pigtail yet just wondering if anybody has used the Ac Delco PT2145

 

[nvrenuf]

So you did use it on your square body truck? I have read a lot of threads i hope some more people can chime in cause I guess if you have an idiot light you have to run a resistor......my truck has a gauge.

I used the pigtail on my 91 Blazer but I was only using it for the CS end plug (my harness was hacked up). I was just saying that the pigtail looked like it would plug everything together perfectly. I did not use a resistor, I think I put a bulb in the circuit (I can’t remember for sure and I’m not home to look).

I had to remake the alternator portion of my harness, I used this diagram.

 

[mavtricks71]

Man it just makes me more confused lol ..... The S wire connected to the alternator stud..... I thought just connecting PT2145 and then just tightening down the original alternator stud wire from my harness was gonna work. ugh

 

[bucket]

Man it just makes me more confused lol ..... The S wire connected to the alternator stud..... I thought just connecting PT2145 and then just tightening down the original alternator stud wire from my harness was gonna work. ugh

Putting the S wire on the Bat stud is optional. It eliminates some potential weak points in the factory harness that could be an issue at some point. The same thing can be done with the stock SI type alternator.

 

[Matt69olds]

It’s preferred to put the connection for the “S” wire closer to the fuse box. That way the regulator will sense voltage closer to the electrical draw.

Having said that, if the electrical system is in good condition with properly sized wiring, there shouldn’t be much difference between system voltage at the alternator verses the fuse box.

Assuming everything works as intended, either way works well.

 

[Jgonick]

Maybe this will help. This is what I've always gone by. From "Alternator Bible" by Bill Ansell

Alternator Bible Link

 

[Jgonick]

The terminals on a CS are PLFS or PLIS. which do you have?

The Ac delco PT2145 should work, but you might have to move the yellow wire over one depending on the alternator's terminals & setup.

EDITED: After looking at the adapter again- It should work no matter what. It appears to have the a resistor in the yellow "Lamp" wire.

 

[82sbshortbed]

I think @82sbshortbed went though this over this last summer?

Yes I used a side marker socket and bulb as a resistor and it works great. Before it wouldn't even crank. Lol

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