10SI Alternator rebuild

[Raider L]

@SirRobyn0, and anyone else interested.
Remove neg. battery cable from battery. Remove alternator from vehicle. The first step is to mark the three sections so that you can keep the "clock", which is the way your alternator is turned on your engine, i.e. how your alt. wires come up. is the power wire on the top, side, bottom, however. Take a small punch and make any kind of dot in all three, the case halves and the stator in the middle.

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Put the alt. in a vice and chuck up on the pulley. It doesn't have to be tight just let it rest on the fan so it's sitting up. The using a 5/16" socket, 1/4" drive sockets for all of this disasymbly, remove all four screws.

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Take hold of this half. This half holds the pulley, fan, front case half. Inside will be the rotor. It is bolted to the pulley so the rotor stays with the front half when you pull the halves apart.

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Take hold of the back half, and you can hold the center section to, that's the stator and pull both halves apart. You may have to wiggle it a bit and when the two halves start coming apart you will hear a click sound from the inside as the brushes come away from the rotor slip rings. Don't worry about this sound it will probably be okay. The brushes will stay inside at the brush block, as you will see, when the halves come apart.

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[BearKing]

Rebuilding those is a fun job. Starters are fun also.

 

[Raider L]

Pull the halves apart.

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Separate the halves and set the front half aside. the only test for it is testing the slip rings the center of the rotor with the shinny rings on the shaft where the brushes run. we'll cover it later.

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Here's what made that clicking sound as you pulled the two halves apart, the brushes, in the center of the pic they look like two rectangular black things with the copper braided wires attached to them. They ride on the slip rings of the rotor and that's what helps make electricity. The springs in the thing that hold the brushes is the "brush block". Those springs will fall out so don't loose track of them. I'll show you next how to put the brushes back in the block so they will stay, and it's much easier when you get the block out than trying to put them in after the whole thing is put back together.

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[Raider L]

Next, remove the nuts holding the stator, three, using a 11/32" socket.

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There might be three little lock washers under the nuts, remove them before lifting the stator out or the washers may pop off the screws and you may loose them on the floor. Lift the stator out and set it aside. You'll be testing it later.

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Using a 1/4" socket remove these three screws. They'll seem to turn and turn and turn but what's happening is they are working their way out of the insulators on the only two screws that have the insulaters on them. Those insulators should be snug in the brush block and their sleeves pass through on into the voltage regulator under the brush block. The only reason to remove them is only if you are replacing the Diode Trio, the part with the three rings on top, the black rectangle, then a long leg going to the brush block. The Diode Trio is a replaceable part and there is a test for it to look for a fault.

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Once the screws are out, the two in the insulators can be loosened up enough, you can feel it when they are out of their holes, and remove the one on the other side. Take the brush block out, and the part under it, that's the voltage regulator. It will be kinda stuck somewhat on the two insulators so it may hold onto the brush block as you lift it out.

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[Raider L]

This is the voltage regulator. It is probably the one part that is the cause of most of the problems with this type alternator, although the other parts do have problems to just not as often as the voltage regulator. Although the Delcotron 10SI is probably one of the most reliable alternators made. I have marked the voltage on this particular voltage regulator. If some of those numbers on the side indicate what the voltage is I don't know what they are. I ordered this regulator because it said it was a 14.7 volt regulator. We'll see.

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To remove this part, it is the Rectifier Bridge use the 1/4" socket. And go ahead and remove the screw holding that capacitor to. You don't have to take out the cap, leave it in it's usually okay.

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Then take a 7/16" socket and unscrew it and remove it. That bolt is where you attach the #12 red wire that goes on in the engine compartment. It's not necessary to take it out, it just pulls out of the hole from the other side of the case, unless there is something wrong with it, like mine, it was burned up and I had to replace it.

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And remove the Rectifier Bridge.
Now the alternator is striped. You can replace the case bearing at this point if it needs to be replaced. You can use a socket from the other side of the case with a hand press.

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[Raider L]

To put the brushes back in the brush block push the end with the braided wire on it first, back into the block. Now, be aware, if you don't get the brush in the hole right off it can slip off the spring, after all the brush is graphite and is slippery, and if it does slip off the spring it can shoot the spring halfway across the room. So do this job some place where you can control things, okay? Ha, ha. These brushes have a little hole near the top of the brush for a pin, to hold the brush in the block by lining up the pin with that hole in the block. You can use a wire, straightened out paper clip, or a small nail. Whatever you use make sure it's at least two inches long. Sometimes you will get an actual pin with a new alternator in the box. If you do, hang onto that sucker, it's handy.

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In this case I've pushed the wire through the hole in the brush block and the hole in the first brush and partway over to the hole of the next brush.

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Next, push the second brush down it's hole, and don't let the brush slip off the spring or you'll be hunting for that spring till midnight, ha. Push the wire, pin, paper clip on through the top of the brush and the other hole in the block and out the other side.

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And there it is, done. In brushes that don't have that convenient hole near the top you'll be pushing the wire, pin over the top of the brush itself. In that case you'll have to push the brush further down the hole in order to get the pin over the top of the brush to hold it in the block. It's easier to use a small screw driver to finish pushing the brush down so you can get the pin over the top of it. And again be aware, that little screw driver can slip off the brush even easier than your fiinger and the spring will shoot even further across the room!

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[Raider L]

Here is where that pin, wire will stick through the back of the case when you assemble the voltage regulator, and brush block, Diode Trio going back together.

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I thought I would include this for GP (general purpose), if you find that you need to correct an under charge condition and the instructions say to put a small screw driver into this hole and touch, ground by touching, this tab on the voltage regulator, this is the tab to touch.

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And when the brush block and voltage regulator is assembled in correct, that tab will be in this hole. You can look at the back of your case and see what it looks like. And it is about 3/4" or so inside. It's kinda scary to stick a small screw driver into the back bottom part of a running alternator that you may not even be able to see that hole clearly enough to stick anything in there. But I thought I'd include what it looks like off the engine so you can see what you're in for. The Diode Trio is just hanging there not in the proper position. Disregard.
And that's it people. To put back together, like they say, go in reverse order. I hope this helps take some of the mystery out of dealing with your alternator and I hope more people decide to rebuild their's and not spend the money buying a new one. You can go to the testing instructions on this site for testing info, and testing is real simple to. It's either showing the correct numbers or it's not. It's not a whole lot of different things that indicate a faulty alternator.
And watch out for that "gen" light on your factory instrument panel when you start your engine. It tells you a lot about what your alternator is doing. It'll come on when you start and then in a few seconds will go off. If it doesn't it's probably the voltage regulator and if it stays on it's probably the voltage regulator. Check the spec's.

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[bucket]

Great thread! I went ahead and moved it to the main electrical part of the forum, and I "stickied" the thread too. Also added 10SI to the title.

 

[squaredeal91]

Great write up!! I've rebuilt 2 of these but it's been quite a while, I bought a regulator to try to fix one of my cores to keep in the scout for wheeling trips a while ago but haven't. I think I'm motivated now lol

 

[Raider L]

I wanted to add a couple of little minor details about these screws. This is the capacitor screw, 1/4" socket but it's the shortest one in the inside.

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This is the screw for the rectifier that is the same as the one's that hold the brush block. So if you have a little pile of screws just remember this one and the brush block are all the same. I have a bag of alternator internal parts and if I need a better screw I know from this size I can use it for any of the internal parts.

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This is the back of the voltage regulator. It's supposed to be an insulator against the case, to protect it from heat.

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This rectifier nut sometimes has this star washer made on it and I've seen some that had just a flange nut. Do not over torque this nut! It just needs to be snug that's all. Also, the bolt that nut goes to will push out. Sometimes the thick insulater part on the back where that bolt goes through the case becomes old and cracked. Check that when you inspect the cases. You can get that insulator part on line.
All internal parts only go one way. There's no way to get them backwards.

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[SirRobyn0]

Yes this is a really great thread and I have enjoyed reading though it. Glad to see it has been stickied as well.

 

[Big Ray]

I put fresh bearings in mine when I do them.

 

[Raider L]

@Big Ray
Usually it's a voltage regulator that goes out sometimes in mine. But after I think, three times I'll take a look at the bearings and then I'll do that to. But I bought a hand press, the kind that has a square part that the handle gearing lowers down on a part? I used to have to take it to work to put new bearings in. but since I became disabled I no longer had access to shop tools. So for a long time I had no way of pressing bearings. And I'll tell you something else that hand press can be used for and that is pressing caliper pistons back into the caliper. The press works real good for that to. Yeah, these days the more we can do ourselves to save money the better. And thos dead gum alternators have got real expensive. I think it's because the higher voltage alteernators for these computer cars are real expensive to begin with. So I guess the remanufacturers felt they could get more for these old alternators to. I remember they used to be about $28 bucks. Now they're closer to a hundred. And the alternators for new cars a over three hundred.

 

[Corvette Ed]

Excellent write up.

 

[Juggernaut]

Great write up! One thing I can add for those who do a lot of 4 wheeling is to spray the windings with red insulating varnish. You can get it on e-bay, about $20 last time I got a can. It helps to shed dirt and mud to keep your windings from shorting out. Moto Finish is the brand I normally use