Rebuild your own alternator? - Chevelle Tech
Electrical & Wiring Troubleshooting electrical problems.

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post #1 of 38 (permalink) Old Sep 8th, 10, 2:17 AM Thread Starter
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Rebuild your own alternator?

Works for me. Here's a series on rebuilding your own alternator. First off: this is not a show car, this car is my daily driver and has been since 1987. The engine was built in 2000, installed in 2001, hasn't been cleaned since. So, it doesn't look like a show car or even a weekend cruiser. Also, please note I'm nor claiming to be an alternator or electrical expert.

This alternator is a rebuilt, a couple years old. After the front end wire harness fried a few months back I checked it and discovered it was putting out almost 15 Volts. Oops, most batteries don't like that, batteries in Az really don't like that. Checked the new harness which is an M&H custom piece modified for a 10SI alternator. What this means is the wiring for the factory voltage regulator is eliminated since the 10SI alternator has an internal regulator. I double checked the harness to make sure it wasn't the cause of the overcharging, it wasn't. The front bearing of the alternator was just starting to be a little noisy too so I ordered up a rebuild kit from DB Electrical, a vendor well known to long timers here. This may not be the exact one but similar. Notice it has a new Stator included and attractive price.

http://cgi.ebay.com/ebaymotors/Delco...Q5fAccessories.


First step always: disconnect the battery. There's a reason for this, I'll post a pic later.



wire plug on the side gives it away as a 10SI, not an original 70 alt, which would have a smaller plug on the back. unhook the 2 wire connector, pull the nut and battery wire off. That nut might be metric, mine was 12mm.



loosen the pivot bolt on the bottom with a 9/16"



loosen the adjuster bolt with a 1/2" or 13mm, whichever it has. Many "original" alternators have been rebuilt at a factory and are now metric thread.



The alternator can then be pushed in and the belt removed. Spin out the adjust and pivot bolts, lift the alternator out.





This spacer is critically important, don't lose it. It's supposed to be bolted to the back of the alt but many aren't. Mine's not, it's the original for the early style alt, bolt tab is wrong for the 10SI type. Important part is the length, for my 70 small block setup it's 3.25".






Tom Terrific or Terrible Tom, depending on the phase of the moon, passing cosmic rays or other factors not fully understood except by my wife.

Last edited by Tom Mobley; Jul 25th, 11 at 5:19 PM.
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post #2 of 38 (permalink) Old Sep 8th, 10, 2:30 AM Thread Starter
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Re: Rebuild your own alternator?

Empty spot where the alt was. Remember what I said about a 10 year old engine in a daily driver? Looks the part. Now, for the eagle eyed among us, what's wrong with this pic?



Moving right along into teardown: hold the fan with a thick towel and hit the big nut with an impact. Mine was 1& 1/8", impact blows it right off. I've done this with a ratchet but it was hard to hold on to the fan.





Notice the nubbin or hub on the back of the pulley.



Fan fell off. The keyway looking recess is not used in this application.




The back of the alt:



This D shaped hole is for testing the alt. There's a metal tab in there, you can reach in with a small screwdriver and short the tab to the case. This throws the alt into full output mode, output can be tested with an inductive clamp.



This rectangular hole turns out to be important during re-assembly.


Tom Terrific or Terrible Tom, depending on the phase of the moon, passing cosmic rays or other factors not fully understood except by my wife.

Last edited by Tom Mobley; Sep 8th, 10 at 4:34 AM.
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post #3 of 38 (permalink) Old Sep 8th, 10, 2:41 AM Thread Starter
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Re: Rebuild your own alternator?

Spin out the four bolts that hold the case halves together. They're all the same, no short or long or weird threads or anything.



Flip it over, pull the front of the case off. Notice the thin spacer ring that falls off the shaft.



This is the front of the rotor, notice the wide spacer ring. Don't mix these up, the wide one is inside the case, the narrow one is outside.



Inside the front case, front bearing retainer:



Three bolts out, retainer falls off, then bearing falls out. This one needed no persuasion, came right out.




Tom Terrific or Terrible Tom, depending on the phase of the moon, passing cosmic rays or other factors not fully understood except by my wife.

Last edited by Tom Mobley; Sep 8th, 10 at 4:35 AM.
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post #4 of 38 (permalink) Old Sep 8th, 10, 3:01 AM Thread Starter
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Re: Rebuild your own alternator?

Here's what we're left with: alt with no front case



Grab the rotor and pull it out. Notice the balance holes drilled in this. This was a DB Electrical piece to begin with. Pretty decent.



What's left inside case after yanking the rotor. The spring loaded brushes are popped out along with the springs. The black plastic piece at lower left is the brush holder. Trapped under it is the white ceramic looking regulator with the two spade terminals sticking out to the left. Center top with the three wires and nuts is the diode trio. The bolt holding it in on the left side is also the battery wire terminal that comes out the back of the case. Lower right is the condensor AKA a capacitor. This drains off any residual AC current to ground and keeps noise out of the radio. All this stuff gets replaced.



Speaking of brushes this is what used to be called a commutator, now called slip rings. The two dark bands are where the graphite brushes ride.



Anyway, pull the three nuts off the the diode trio and lift off the connector to the brush holder, then lift out the stator. Some guys might still call this a field coil, but that's really part of a generator.




Pull the condensor, notice the mount bolt is different.


Tom Terrific or Terrible Tom, depending on the phase of the moon, passing cosmic rays or other factors not fully understood except by my wife.
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post #5 of 38 (permalink) Old Sep 8th, 10, 3:18 AM Thread Starter
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Re: Rebuild your own alternator?

Run the nut off the stud holding the left side of the diode trio. It comes out the back, it's also the Battery terminal.



view from the back:



Notice the three bolts holding the brush holder and regulator. Two of them have an insulating sleeve and one doesn't. The one that doesn't is the one closest to the case.




Remove the insulated bolt holding the connector between the stator and brush holder, set it aside. Pull the other, smaller bolt holding the diode trio, lift it out and set aside.




At this point the regulator is just sitting there, take it out and set aside.




Support the back half of the case and drive the rear bearing out. This was actually the hardest part of this whole job. That thing was tight in there, I had to really hammer it with a dead blow hammer.




Tom Terrific or Terrible Tom, depending on the phase of the moon, passing cosmic rays or other factors not fully understood except by my wife.

Last edited by Tom Mobley; Sep 10th, 10 at 10:53 AM.
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post #6 of 38 (permalink) Old Sep 8th, 10, 3:52 AM Thread Starter
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Re: Rebuild your own alternator?

Mockup of the rotor, spacers and bearing. Wide spacer and bearing are inside the case, narrow spacer and fan are outside.




Clean up the slip rings with a little 600 grit wet-or-dry. No, I'm not using the paper inside out, it's folded in half.








Cleaned up the case with can of spray brake cleaner. Alternator wasn't that old and clean up was easy.



New parts in kit. Notice the rear bearing is not there. It's in the freezer. The bore where it goes was honed out with a wheel cylinder ball hone. The rear case was heated with a heat gun before pounding/pressing the new bearing in.





Used the old bearing to drive in the new one. As tight as this fit I didn't want to take a chance to hitting the new one directly.



New bearing in. Notice it's pre-lubed and a lip seal to keep it clean.


Tom Terrific or Terrible Tom, depending on the phase of the moon, passing cosmic rays or other factors not fully understood except by my wife.

Last edited by Tom Mobley; Sep 10th, 10 at 10:35 AM.
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post #7 of 38 (permalink) Old Sep 8th, 10, 3:52 AM Thread Starter
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Re: Rebuild your own alternator?

New brush holder. DB Electrical supplied it already assembled with a piece of wire holding the springs and brushes in. A small thing but it helps.



Install the regulator and brush holder loosely with the one bolt that's not insulated. It's the one nearest the case.



flip the rear case over, install the install the battery wire terminal and it's insulator from the back. Turn it over again and set it on the counter on the stud.





Set the diode trio in and install the stud nut and the smaller bolt. Tighten them up.



install the connector piece and the other two insulated bolts in the brush holder/regulator assembly. TIghten them up. Set the stator in, align the cutouts in the O.D. with the 4 bolt holes for the case bolts. Hook up the three wires, tighten up the nuts. I had to "adjust" the wire terminals on the new stator so they would fit over the studs.





Install the condensor. I had to fool with the bolt that goes through the wire terminal into the diode trio. It threaded in very tight, I back ed out and started over several times. Used a little drop of oil on the bolt threads, I thought it was going to break off it turned so hard.


Tom Terrific or Terrible Tom, depending on the phase of the moon, passing cosmic rays or other factors not fully understood except by my wife.
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post #8 of 38 (permalink) Old Sep 8th, 10, 3:57 AM Thread Starter
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Re: Rebuild your own alternator?

clean the rotor and slip ring surfaces and set it in. On this one the shaft was a tight fit in the rear bearing seal and wanted to pop back up due to air pressure in the bearing. Gave it alittle time and wiggled it some, fell in.



Notice the relief in the stator aligned with the bolt hole in the case.



Install the new front bearing in the front case:



Tom Terrific or Terrible Tom, depending on the phase of the moon, passing cosmic rays or other factors not fully understood except by my wife.
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post #9 of 38 (permalink) Old Sep 8th, 10, 4:05 AM Thread Starter
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Re: Rebuild your own alternator?

Set the wide spacer on the shaft:



Set the front case on ans start a couple bolts from the bottom. I had to work with it a little to get it on straight and lined up with the bolt holes. No biggie.





I set it upside down on a vise and tightened up the bolts in a criss-cross pattern.



Front view:



dropped on the narrow spacer:



Install the fan, pulley, lockwasher and nut. Note nubbin/hub on back of pulley against fan.







Tighten up the nut with an impact and a towel just like taking it apart to begin with.


Tom Terrific or Terrible Tom, depending on the phase of the moon, passing cosmic rays or other factors not fully understood except by my wife.

Last edited by Tom Mobley; Sep 8th, 10 at 4:42 AM.
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post #10 of 38 (permalink) Old Sep 8th, 10, 4:13 AM Thread Starter
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Re: Rebuild your own alternator?

Remember the little wire in the brush holder?



Pull it out, you can hear the brushes pop in against the slip rings



Back on the car, a little juggling with the pivot bolt and spacer since it's not properly bolted to the back of the case. Hook up the wires, make sure the battery wire is good and snugged up, bad place to have a loose wire.





Belt tightened up, adjuster right in the middle of the travel, good.



Battery voltage, engine off



Battery voltage, engine running. No more overcharging, just right. Acceptable range is 13.8 to 14.2. I'll buy it at 14.0.


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post #11 of 38 (permalink) Old Sep 8th, 10, 4:15 AM Thread Starter
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Re: Rebuild your own alternator?

Checked the dash light, working OK. I think it took longer to post this up than it did to do the job. Double check pivot and adjuster bolts and the belt, all tight.

Tom Terrific or Terrible Tom, depending on the phase of the moon, passing cosmic rays or other factors not fully understood except by my wife.
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post #12 of 38 (permalink) Old Sep 8th, 10, 4:30 AM Thread Starter
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Re: Rebuild your own alternator?

ELcoman, you win whatever the prize was. I loaned my killer Q-jet to a buddy and have a temporary carb installed. The factory fuel line didn't fit so I rigged a hose. Have to pull the water pump to get that hardline out so there it sits.

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post #13 of 38 (permalink) Old Sep 8th, 10, 9:24 AM
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Re: Rebuild your own alternator?

A great thread Tom!! Nice work.
I hadn't rebuilt an alternator in years...this was a good refresher. Excellent photos.

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post #14 of 38 (permalink) Old Sep 8th, 10, 1:02 PM Thread Starter
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Re: Rebuild your own alternator?

At the beginning of this thread I said something about always disconnecting the battery. Well, I was working on a carburetor on a friends truck Sunday. His alternator doesn't have that little rubber boot over the battery post on the back of the alternator. Dang. Shorted out my metal watch band, couldn't get that thing off fast enough. it was 105 out, arm and hand all sweaty, perfect for instant heat transfer to skin.
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post #15 of 38 (permalink) Old Sep 8th, 10, 2:10 PM
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Re: Rebuild your own alternator?

GREAT THREAD Tom!
But shouldn't it be in the Tech Reference section?

I still can't wear my watch on my left arm after all this time since I shorted the band out on the alternator post.

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