Delco CS130 Alternator Installation

Discussion in 'Diesel Tech' started by RD Durham, Jun 12, 2007.

  1. RD Durham

    RD Durham High Wheeler

    While the diesel Traveler was down and awaiting parts I decided to install a hydraboost unit and a Delco alternator. The first alternator I installed in place of the Hitachi alternator was a 63amp Delco 12si. I had to file off a lot of metal from the bottom of the adjusting arm but nothing to serious. For my mounting bracket I basically used some plans that were previously posted on the web site - Diesel Forum. I used the plans posted in this thread as the basis for my bracket. Instead of flat plate I used angle iron and some 1/4" plate.

    Thread that includes an alternator bracket plans:

    Another thread that has a different bracket design:

    After fabricating a mounting bracket everything looked good except for two really minor points. The top of the adjusting bracket ended up just touching the lower radiator hose. Some additional filing on the top and bottom of the adjusting arm cured this headache. Also, doing some reading on the BB diesel forum, it seemed that there were some on here that were a little disappointed in the inability of a Delco SI alternator to charge at low speed or idle on the SD-33 diesel engine. So that got me to thinking some and since I was still waiting on parts and such, I decided to experiment.
    Last edited: Jun 13, 2007
  2. RD Durham

    RD Durham High Wheeler

    Bracket picture

    Picture of my final bracket design.

    Attached Files:

  3. RD Durham

    RD Durham High Wheeler

    Choice of Delco CS Alternator

    On my 1980 Terra, with a 392, I'm running a Delco CS144 140amp alternator and it works pretty good, especially at slower speeds. So I figured a Delco CS alternator should also be a good choice for a diesel Scout II. I am not sure about the Hitachi alternator, but a Delco SI alternator has to get up to around 7000 rpm on the alternator shaft to put out it's maximum amperage. A Delco CS alternator has to get just under 4500 rpm on the alternator shaft when it reaches full amperage. Engine RPM may vary because of the alternator pulley diameter, the smaller the pulley the quicker the alternator can get up to maximum output, so trying to estimate what the engine RPM would be at full output takes a little more thought and figuring than I'm up to right now. With some exceptions, the CS and SI alternators use the same size pivot point/hole on the alternator case, so I can reuse the bracket I made for the Delco 12si alternator. The Delco CS style alternators also have some other advantages as they are normally a quieter alternator to run producing less static. The CS alternator also has a better design for dissipating heat with two cooling fans, and it comes in much higher amperages up to 140amps in some cases. Downside is a CS alternator is a lot more expensive as a rebuilt unit and normally will sell from $90 to $130, while a SI unit will be $30 to $70 depending on amperage/manufacturer(rebuilder). The other more specific downside is I can't use a CS144 alternator in the stock location on a Nissan diesel engine. A Delco 12si alternator measures 6.6 inches from the pivot hole to the adjusting hole, which is pretty close to the size of an Hitachi alternator, the Hitachi being slightly smaller I believe. (I took measurements off the Hitachi alternator before I sold it, but they seem to be lost in my filing system somewhere.) A CS144 is a larger alternator and is approximately the same size as a Delco 15si or 17si and is 7 inches from pivot hole to the adjusting hole in most cases. However, there are other alternatives when it comes to CS alternators. There are also the CS121, CS130 and the CS130D. The numbers following the "CS" refer to the diameter of the alternator case in millimeters. A CS121 is 121 millimeters in diameter which is around 4.76 inches across, a CS130 is about 5.12 inches and a CS144 is 5.67 inches. That's the diameter of the case not the distance from the pivot hole to the adjusting hole. For comparison a Delco 12si alternator case diameter is 5.3125 inches across and a Delco 10si is approximately 5.125 inches in diameter.

    A CS121 is normally considered a slightly harder alternator to rebuild and is not as common to find in the salvage yards. A CS130 is pretty common in the salvage yards. A CS130D is a much different animal from the CS130, and it is much harder to rebuild. You also have to be very careful how you wire up a CS130D alternator as they are specific as to whether the vehicle has an "idiot" light or not. Wire it up wrong and you've blown away about $200. I've been told that for the other CS alternators that if you wire them up incorrectly they just won't work, but I've not tried that out to be sure and it may be just so much speculation. Since I really don't know much more about a CS130D, I decided to stay away from it, plus I haven't seen too many in the salvage yards anyway. So I decided to look at a CS130 alternator. From what I've seen the amperage ratings on a CS130 go from 61amps to 105 amps. For more information see:

    Website information sources:

    One last note on a possible downside, you really need to be sure that a CS alternator has room to draw in fresh air. These alternators have the ability to push a lot of air through the case to cool the components, but if the alternator is buried in the wiring, hoses and such it won't be able to draw in enough air and will burn out. However, this doesn't seem to be an issue for a Scout, as mounted on my diesel Scout, and on my Terra (under the AC bracket) the air flow has been no problem.

    I choose a 105 amp CS130 alternator with the adjusting arm bolt hole 180 degrees out from the pivot point hole, same as a Delco SI alternator. I also choose one with the smallest adjusting point ear that I could find. I then used a double pulley off of a Motorcraft (Ford) alternator for the v-belts. I first used a single pulley but the distance between the alternator pulley and the v-belt for the power steering pump was pretty close. I swapped in the double pulley to keep the two belts separated and to keep the power steering v-belt from getting chewed up by the pulley on the alternator. So far no complaints, though I do need to get a narrower belt for the alternator, see pictures posted later in this thread.
    Last edited: Jun 13, 2007
  4. RD Durham

    RD Durham High Wheeler

    Alternator Pictures

    Attached are pictures of some of the alternators I looked at for this project. On the left is the Delco CS130 alternator that I used for this project. In the middle is the Delco 12si alternator that I installed before the CS130 alternator. The right alternator is a Delco CS144, that is a spare for my Terra with a 392 V8. The pivot points are at the top of the picture, while the treaded holes for the adjustment arm are at the bottom.

    Attached Files:

    Last edited: Aug 27, 2010
  5. RD Durham

    RD Durham High Wheeler

    Issues and Headaches

    There are a couple of other issues with a CS alternator that you need to be aware of that can come up and they are minor, at least for me. First, a CS alternator is used in a serpentine belt system and is mounted fixed, non-adjustable to the engine. Since the CS alternator is not meant to be used with an adjusting bracket I found that one of the case bolt forgings on the front case half interfered with the adjusting arm. To get the pulleys to line up I had to run the adjusting arm, mounted to the water pump, on the back of the threaded adjustment point on the CS130 alternator. I ground off 1/8ths inch off half of the top of that part of the casting on the front case half and that, with also grinding off some from the bottom of the adjusting arm, got the alternator to adjust without a problem. Second issue is that the CS alternators were used in a wide variety of engine applications. While it's still the same alternator the mounting ears/points on the front halves of the case will vary. Some points are not 180 degrees apart and some of the front cases have three mounting points. Even when you have the pivot and adjusting arm points that are 180 degrees apart sometimes the adjusting arm point is really tall. The alternator may also have two pivot points, one on the front case half and one on the back that have to stay aligned, so case clocking is impossible. However, most CS alternators can be clocked just like a Delco SI alternator. If you want to add a CS130 alternator you would want to make sure you get an alternator with the short adjusting arm point and single pivot point and that they are 180 degrees a part. Also, most CS alternators use a threaded post and nut for the BAT terminal that is similar to a Delco SI alternator. However, though they aren't as common, some CS alternators came with BAT Terminal that is a post with a threaded hole for a small bolt. These are still usable but you have to make adjustments for your wiring to the BAT terminal.

    Also, once you have modified the front case half for a CS130 alternator it then doesn't matter which front case half design comes with a replacement CS130 alternator. Just swap in your modified front case half for the front case half of the replacement alternator.
    Last edited: Jun 12, 2007
  6. RD Durham

    RD Durham High Wheeler

    Adjusting Arm and Case Alterations

    Pictures of the adjusting arm and case alterations that I made.

    Attached Files:

  7. RD Durham

    RD Durham High Wheeler

    Wiring Issues

    When you go to mount up the CS alternator to a Scout II you have to make a decision as to the wiring. Option one, wire in a CS plug into the stock wiring. Option two, wire in a SI plug into the stock wiring and then use a pigtail adapter to go from the SI plug to a CS plug. With a diesel you not only have to decide do I want to wire up the CS alternator plug or do I want to wire in a Delco SI alternator plug, you also get to do a rewire from the Hitachi alternator/remote voltage regulator to the CS or SI internally regulated alternator.

    Since a diesel Scout doesn't have a Delco SI plug to start with, you have to wire in a Delco SI or CS alternator plug. I wired in a Delco SI plug for one reason, if the CS alternator goes out far from home I can drop in an inexpensive Delco 10si or 12si alternator to get me home. A rebuilt CS alternator will cost in the neighborhood of $100 or more while a Delco 10si or 12si will cost approximately $35, give or take, for a rebuilt unit and SI alternators were used on a ton of GM cars and trucks. With my fabricated system even using a CS alternator, I know a Delco 10si or 12si will be a direct drop in with my alterations and will plug right into the wiring loom I fabricated, once I remove the SI to CS adapter. Other than that I'd just wire in the CS alternator plug and be done with it. If you wire in the Delco SI plug you have to buy or make an adapter to go from the CS alternator to the Delco SI male plug. You can get an adapter at Advance Auto or NAPA for around $25. The adapters comes with a resistor or without a resistor, so you have to decide which to use. If your application uses an "idiot" light, or an line wire resistor (ala Scout II gas engine trucks), you choose a non-resistor adapter (that is the adapter doesn't have a built in resistor). Otherwise you choose the resistor adapter. I added in a "idiot/charging" light to the diesel Traveler so I bought a non-resistor adapter. You can also use a resistor adapter even if you have an "idiot/charging" light or resistor wire, so long as the total resistance in the circuit doesn't exceed 350 ohms.

    Non-resistor adapters:
    - AC Delco: 8077
    - NAPA: ECHEC80

    Resistor adapters:
    - AC Delco: 8078
    - NAPA: ECHEC82

    A Delco SI plug "pigtail" can be purchased from most auto parts stores or found in a salvage yard. To wire in the Delco plug into a diesel Scout you need two wires a key on hot and a wire for constant battery voltage. Once you pull all the wires for the Hitachi alternator and voltage regulator you should have two left over wires at the firewall. Looking at the wiring diagrams, I was able to see that one is key on hot and the other a constant hot. The "IG" wire on the Hitachi voltage regulator is a key on hot wire and the "A" wire is a constant hot for the Hitachi alternator. The plug on the Hitachi voltage regulator is normally marked as to the which wire is which, having lables for "IG", "F", "A", "E", "N" and "L". You still need to use multimeter to see which is which. The key on hot for the Delco SI alternator is for the plug wire marked "1" or "F" on the SI alternator case, and the constant hot is for the plug wire marked "2" or "S" on the alternator case. The wire from the "2" plug can be bolted to the BAT terminal on the alternator or taken directly to a battery cable lead. The wire for the "1" side of the plug has to have at least 35 ohms resistance in the wire. The resistance can be supplied by a 12v light bulb, in-line resistor or a combination of both. After that you just plug in the male Delco SI plug into the SI to CS adapter and then plug the adapter into the CS alternator.

    Wiring in the CS plug, without an adapter, isn't difficult. Just like the SI alternator, you still need a key on hot wire and a constant hot wire. The CS plug you can get from a salvage yard or auto parts store will have anywhere from two to four wires. Where the plug fits on the alternator the socket will be labeled "S", "F", "L" and "P". Sometimes the terminal that is labeled "F" may be labeled "I". However, for my purposes it makes no difference as to "F" or "I" because for a Scout II you only use the "S" and "L" wires. (NOTE: Some CS alternators have an "I" in place of the "L" wire. You don't want to use this alternator as it has to be wired differently. They aren't very common but do double check if you pull one from the salvage yards.) The "S" wire connects to a constant hot 12v source and can be connected to the BAT terminal on the alternator. The "L" wire is a 12v key on source that needs at least 35 ohms resistance in the wire. Same as a Delco 12si alternator. Again the resistance can be supplied by a 12v light bulb, in-line resistor or a combination of both. The line resistance for the "L" wire has to be between 35 ohms to 350 ohms. If the resistances is more than 350 ohms (for either the SI or CS application), then there is excessive resistance somewhere in the circuit which needs to be isolated and repaired before proceeding any further.

    For my setup I bought a generic red dash light from NAPA that had 34.5 ohms resistance as measured with my digital multimeter. In testing my wiring from the battery, through the ignition switch and to the end of the stock wiring at the alternator I have 1.7 ohms resistance, so I didn't need to added in an additional in-line resistor along with the light bulb. For my set up I added additional wiring to the end of the stock wire, routed it back through the firewall to my "idiot" light" and then back through the firewall to my SI plug. It is important that you have at least 35 ohms resistance when using an "idiot/charging" light as otherwise the alternator will not engage for charging your battery.
  8. RD Durham

    RD Durham High Wheeler

    Final Setup Pictures

    Attached are pictures of the final setup. As you can see I do need a much narrower belt for the alternator. What is being used right now is the stock alternator belt for the Hitachi alternator.

    Attached Files:

  9. RD Durham

    RD Durham High Wheeler

    Final Thoughts

    In using the CS130 over the last few weeks I've had no complaints. The alternator will very quickly come up to full charge at idle after starting. With an SI alternator you would probably have to "blip" the throttle to get the alternator to spin up enough to start charging. Since the alternator was 105 amps I also added in a shunt wire from the alternator BAT terminal to the battery positive post, in addition to the stock charging wire. This means that the AMP meter on the dash won't read correctly. It will work but the deflection of the needle on the meter will be less because the charging current is now running through two wires, the stock charging wire and the added shunt wire. The decrease in the needle deflection on the AMP meter will be proportional to the total resistance of the charging wire in relationship to the shunt wire. If your shunt wire is the same gauge as the charging wire the decrease in needle deflection will be roughly half. Note though that you will probably have more resistance in the charging wire circuit because of the length of the wire, bulkhead connection, ignition switch, etc. that you won't have in the shunt wire circuit, so total deflection of the needle on the AMP gauge will probably be more than half of what is was in stock form. I also added in a voltage gauge to be able to check the function of the alternator in addition to the stock AMP gauge and the "idiot/charging" light. The truck is being used by my teenage daughter and she needs all the help she can get. :yes:

    On a side note the white wire on the CS plug at terminal "P" is used by GM to run a tachometer off the alternator. This terminal produces a 12v square wave signal that can be used by a tachometer. I've yet to find out just how to do this with an aftermarket tachometer, but it is something that I am trying to find an answer to so I can add a tach to this truck. So if someone has any ideas let me know. I've asked around on some of the GM/Chevrolet diesel forums that I'm a member of and no one there has come up with any ideas for using an aftermarket tachometer with this wire on the CS130 alternator.
    Last edited: Jun 13, 2007
  10. bbellster

    bbellster Farmall Cub

    Thanks for the great writeup. What vehicle should I be looking at for a cs130? It really sounds like the berries, and I've been contemplating the alternator swap sometime soon.
  11. RD Durham

    RD Durham High Wheeler

    Delco CS130 Alternator

    Delco SI alternators were phased out by GM starting in 1985 in favor of the CS style alternators. The first CS alternators after 1985 had some issues with heat so I don't really pay attention to any GM cars before 1990, but that's not to say you wouldn't find a good one in a salvage yard off of those years of GM cars. When I'm in the salvage yards I usually look in GM cars from 1990 to 1995, give or take. This alternator came off of a 1991 Buick Skylark with a V6 engine. It had a remanufactured tag from Advance Auto and it was nice and shiny while the rest of the motor was covered in oily dirt. So I was pretty confident it was in good shape. However, I did run by a local NAPA shop on the way home for a free test of the alternator just to be sure.

    The pulley came off a late 1970's Ford pickup.
  12. dick ardrey

    dick ardrey Binder Driver

    I have had a similar problem . My ORT is a sd33N/A and the alternator is like you describe.
    I think car tacks are looking for a spike from the ignition. Get a tach that is full scale 4000rpm.
    Take your alt. wire and put a small capacitor in line with it. This will electrically integrate the square wave pulse into a spike!! That is what I did and it has been working for 5 years.

  13. RD Durham

    RD Durham High Wheeler

    Thanks. Do you remember what size capacitor?
  14. CareyWeber

    CareyWeber Diesel Herder / Moderator Staff Member Moderator


    Great write up!!!!!!!!! :cool:

    What makes the CS121 hard to deal with / rebuild? I had thought of it because it is smaller and would leave more room for the power steering unit.


  15. dick ardrey

    dick ardrey Binder Driver

    I forget but it is small. Maybe an electrolytic I will check and post later. The size of the spike
    is not important, the important thing is that it is a spike. I remember just using something laying around the junk box. I also did this (like you ) in frustration and had my scope outside looking at the wave-shape, before and after. A large disc type , like the one on the gauge CVR it is I think .1mf . Try that, all you want to pass is the initial positive rising edge of your square wave. If it does not work go larger to a polarized electrolytic of say 2.2uf. Use a cap rated for 25v on your 12v spike.
    I will look when I get home.


  16. RD Durham

    RD Durham High Wheeler

    I've only found one CS121 in the salvage yards in the last three years. I think the biggest issue is that they just weren't used that much. Looking at a schematic breakdown of a CS121 they really aren't that much different than a CS130. Major difference is that the CS121 only has one cooling fan, while the CS130 has two. My understanding is that the CS121 came out first and had issues with cooling, so Delco came out with the CS130. The CS130 had a slightly larger case to help with getting rid of heat and a second internal cooling fan. The one headache with rebuilding a CS121 or a CS130 is that the stator is soldered to the rectifier, where as in Delco SI alternators the stator is attached to three threaded posts using nuts to attach the stator to the rectifier. You have to remove the solder on a CS alternator to get it apart and be careful not to get the rectifer hot. The rectifier is usually a pretty expensive part upwards of $50 to $75 give or take. Not an easy task to get rid of the solder and save the rectifier. Also, when I've tried to find parts for a CS121 it's been a lot more difficult than finding parts for a CS130 or CS144. None of the CS alternators are easy to find parts for, but the CS121 is a lot more difficult. The Delco SI alternators are in comparasion a snap to find parts for in a rebuild. I'd like to find another CS121 to play with, but with the CS130 fitting well and working without a problem it will be one of those future projects.

    The one alternator that I would stay away from is the CS130D. The biggest headache with it is that it is self regulating as to heat. If it gets too hot it stops charging until it cools down. This apparently was a safety feature that Delco built into the alternator to make customers happy, but it ended up having the opposite effect. When the CS130D came out there were a lot of cars sitting in hot summer traffic that all of a sudden were running on batteries. Really big problem in a place like Phoenix or Dallas. As noted above if you also get the wires on a CS130D mixed up it will burn itself out in a heart beat and it's usually a more expensive alternator to replace.
    Last edited: Dec 10, 2007
  17. dick ardrey

    dick ardrey Binder Driver


    My capacitor is a tantalum, 01 uF or 723000 pF @ 25+ volts

    It looks like a chick-let Its in line to the tach input pulse.

    I think any .01 disk @ 25v will work. I just, had this.

    You want to use something that moisture will not get to , hence the tantalum; I guess.

  18. RD Durham

    RD Durham High Wheeler

    Thanks. I really appreciate the information. Next payday I may see if I can find one. Doesn't sound like something that Radio Shack would stock anymore.
  19. RD Durham

    RD Durham High Wheeler

    Addendum One

    This is a picture of the back of a Delco SI alternator. The plug socket is at the top note that it is labled "1" and "2" as well as "R" and "F". The "R" is also sometimes labeled "S". Also shown is the plug in relationship to the socket as well as being inserted into the socket. Note, just in case it's not apparent, that the tab on the plug goes into the slot of the socket, but then most of us probably knew that already.

    Attached Files:

    Last edited: Dec 10, 2007
  20. RD Durham

    RD Durham High Wheeler

    Addendum Two

    More pictures of the plug and such.

    Attached Files:

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