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Discussion Starter · #1 · (Edited)
When I did this conversion there wasn't a lot of condensed info out there, and I looked quite a bit. What I want to do here is provide an easy guide to changing out your 12v generator for a Delco Remy CS130-style Alternator, and clearly explain how to wire it.

If you've looked much online, you'll see there are a lot of kits out there that will provide everything you need to make the swap. (1) (2) (3) These all have three or four basic items that you can easily source yourself for a lot cheaper than the kit price: The alternator (which can be found at any salvage yard for $20), The bracket (which you can build yourself or purchase separately (1) (2)), The wiring harness (get it from the salvage yard or Amazon for $10), The 5/8" Vee belt pulley, and sometimes a belt.

Section 1: Picking an alternator

A lot of people want to run a "one wire" alternator for the perceived simplicity of it, but there are a lot of good reasons to run a 3 or 5 wire alternator instead. (I believe those would be the 10/12 SI alternator and newer CS-130 styles, respectively.) One-wire alternators require you to hit a certain RPM before they begin charging, cannot detect voltage from a remote location, and are more difficult and expensive to acquire. All those problems are solved with a 3/5 wire alternator, and you only need one or two extra wires that are not difficult to install. All of the one, three, and five-wire models are internally-regulated and do not need a regulator mounted on the firewall.

With that being said, head on over to your local salvage yard and look at their Chevy alternator collection. Mine is a 5-wire style that came from an '86 S10. The main thing is to be sure you grab one that has the mounting points 180 degrees apart from each other and has either the 2-pin or 5-pin harness clip. Check out the kits listed above for good photos of what you're looking for. Here's another site with additional info and pictures.

This is a photo of my alternator and cables I picked up for $30 in total. I just went down to the trucks and snipped off some wires. I've already removed the serpentine pulley.

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This is what the back of a 10/12 SI will look like with the double-pin connector. This is called a "3 wire" because there are a total of three wires going to it - two in the pigtail and the single large cable going to the battery.

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And here's the connector on my CS130. Four wires in the harness and one going to the battery make this a "5 wire."

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Step 2: Wiring it up

With either style of Delco Remy alternator you only require one wire other than the battery cable - this will engage the alternator and provide an indicator light to show that it is charging properly. This wire will connect to pin 1 of the 12SI (as shown above) or the "L" terminal of the CS130. To wire this circuit, you will run a small (18 awg will work fine) wire from the ignition terminal of your ignition switch to one leg of a 194 lamp holder. You will then run the other leg of the lamp holder to the pin 1 or L terminal of your alternator.

I was able to trim the lamp holder to fit perfectly in the factory "amp" light socket in my gauge cluster.

Motor vehicle Fender Rim Gas Electrical wiring

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It is possible to use a small resistor in place of the light, but the light itself does serve a useful purpose. If lit, you will know the alternator isn't charging for whatever reason - perhaps the alternator failed, the belt came off, or even that the engine died.

Why not simply run an ignition wire straight to the terminal instead of using a lamp or resistor in the circuit?
When the alternator is not rotating, the L terminal is grounded. That is why the lamp will illuminate when the engine isn't running - there is a difference of potential (voltage) between the hot ignition wire and the L terminal of your alternator. When the alternator starts turning and generates energy, the difference of potential goes away and the light turns off. Without a lamp or resistor to absorb this energy at rest it can cause damage to the internal voltage regulator. You may notice some of the bolt-on kits do not utilize an indicator lamp - this is because their included wiring harness will have a resistor in-line to protect the voltage regulator.

Optional sense lead: On either pin 2 or the S terminal you can connect a 14 gauge wire and attach it either at your fuse block or main junction. If you have an extra-long cable going from the battery to the fuse block you may lose one or two volts by the time it reaches your accessories due to wire resistance. This "sense lead" will read the voltage at this junction and increase the output accordingly. If you have dim headlights, this can help remedy the problem. My fuse block is attached approximately 8 inches away from the battery, so I didn't see any need to attach it.

Note: A CS130 alternator will automatically detect voltage from the wire going to the battery if no wire is hooked up the "S" terminal. Some diagrams show a pigtail that simply attaches from the S terminal to the battery connection, but this is not necessary. I cannot confirm if this is also true for the 10 and 12 SI alternators, however. In the black and white diagram posted above you can see a pigtail attached from pin 2 of the wiring harness to the battery feed cable. This may or may not be necessary.

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I already mentioned I just picked up some spare cables from the junkyard. The positive cable running from my alternator to the battery is, I believe, a 6 awg cable with a fusible link already attached. I snipped this off a late 80's S-10. If you don't have a fusible link you'll want to run something like a 100 amp breaker between your alternator and battery. I also ran a heavy-gauge ground cable from the alternator's body to the negative post on my battery. However, if you want to purchase some extremely high-quality cables at a great price (or just the lug terminals as seen on the + side of my fuse block) check these guys out.

Step 3: Bolting it all up

This was easily the most frustrating part of the job for me. I purchased the lower mounting bracket from Kaiser Willy's as shown in the kit, which incidentally is the same item you can purchase here. But as it turns out, it's cheaper with shipping to get it from Kaiser Willy's. (You'll just have to order the piece over the phone or add it to an existing order because it isn't linked directly on their website.)

You should already have your new pulley hooked up to your new alternator at this point, so you can begin struggling to adjust the bracket so the pulleys will all line up. This is just how I did it - if you want to try any of the other options or roll your own, be my guest.

This is how mine looked after the final adjustments. I used 5/16 bolts through the existing mounting ears on the engine and had to slide it up and down to get the pulley angle just right. It'll take patience and beer.

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And I finally ended up with something that looked about like this. I'm using the stock replacement vee belt here from Kaiser Willys.

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There are a lot of options for upper brackets as well, none of which I've tried. Instead I opted to heat and twist my factory bracket around like a pretzel until it fit where I needed it. I also had to clear the aluminum housing of the alternator a bit so the bracket would sit in the right place.

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And we didn't purchase enough washers to make up the gap between the alternator mount and the bracket, so I cut down a cheap 12-point socket for the job. Note that this tapped hole in the alternator is M8x1.25.

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Grand Finale

I hooked up an autometer volt gauge with the + terminal hooked on my ignition switch, but it doesn't seem to be the most accurate. It was reading close to 16 volts when I revved the engine. Checking across the battery terminals with my Fluke multimeter I got about 13.1 volts at idle and 13.8 volts revved up, which is basically as perfect as it gets.

I hope this guide will make your swap easier to understand and implement. I'm about to graduate with my degree as an industrial electrician, so I found this to be a fun side project. Feel free to ask questions or to point out any errors or relevant info I may have forgotten to include.

Premium Member
9,468 Posts
Your 3 wire diagram is of a 2 wire. Where it says "Add Jumper" you can take this out and run a wire from the solenoid to the number 2 terminal. This is a sense wire so that the regulator will maintain voltage at the solenoid, negating losses from solenoid to alternator whilst under load. This will then be the 3 wire setup.

88 Posts
Discussion Starter · #4 ·
Your 3 wire diagram is of a 2 wire. Where it says "Add Jumper" you can take this out and run a wire from the solenoid to the number 2 terminal. This is a sense wire so that the regulator will maintain voltage at the solenoid, negating losses from solenoid to alternator whilst under load. This will then be the 3 wire setup.
Even though the final setup may have one, two, or three wires coming from the alternator, the alternator itself is still referred to by how many wires it accepts. I've only ever seen these alternators referred to as 3 and 5 wire models.

You can definitely run your sense wire to the starter solenoid if you want, but the end goal is to maintain operating voltage at your accessories and instruments. This article gives a much better explanation for it.

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