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bherder
 
  Rebuild your Alternator (A 'How To') - Posted: 04-23-2008, 10:00 AM
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Post #1

HOW TO REBUILD YOUR ALTERNATOR


This is an instructional for rebuilding older Mopar alternators. I will be rebuilding one of the 100+ amp alternators, but the steps taken are almost identical to the smaller amp alternators.

If you have one of the big alts and you need a rebuilt one, or simply want to swap over your smallish one for one of the ‘big guns’ you’ve probably noticed how expensive they are. I’ve seen them anywhere from about $100.00 to $200.00 at parts stores …. Not cheap! I picked up an alt at the local ‘Pull your own parts’ junk yard. I didn’t need it, but it was there and it was $10.00
I thought, being as I plan on putting a remanufactured engine in my Powerwagon this summer, I’d go through this one, get it all ready to go and see if I couldn’t ‘pretty it up’ a bit.


Depending on how far you want to ‘rebuild’ it, you can rebuild your own for about $40.00

(I bought my parts online.. $20.00 for the drive-end bearing … $5.00 for the commutator end bearing … $9.00 for a brush set)

You WILL however need either a special pulley puller OR a BIG 3 jaw puller. The 3 jaw puller works fine, so if you already have one or can borrow one, you’re way ahead of the game…. You also need a smallish 2 jaw puller for the drive end bearing.

I’ve found two different types of pulleys on these. Even a mix-n-match on the two types of alts. The kind of pulley on the small alts, you can buy a puller at a ‘Harbor Freight’ type of place. Yes, they’re cheap tools, but I bought one, because I don’t do this for a living. I’ve done it enough, however.. If I was in the business, of course I’d buy a quality tool. There is a special puller for the large alt type of pulley, but as I say, a 3-jaw puller works fine for someone who may very rarely do this.

OTHER TOOLS NEEDED

5/16” socket - 11/32” socket – ¼” socket – ratchet and extension – screwdriver – BIG hammer – some sort of abrasive for cleaning – 11/16” deep socket – wood block – misc small hand tools

PARTS NEEDED

See article








Before you start to disassemble the alt, I would highly recommend soaking the four 10-24 screws (Three on the small alts) that hold the casing halves together with some PB Blaster. Chances are they haven’t been removed in eons, and it doesn’t take much to break them. Should you break one (As I did on this one) it’s not the end of the world, you’ll just have to drill and tap the hole. It is kinda’ a pain though.

To do a ‘basic’ rebuild you’ll need three parts. (I’ll explain later the difference between that $100.00 ‘rebuilt’ and the $200.00 ‘rebuilt’)
The ‘Drive end’ bearing (BCA # 303SS) – A ‘Commutator end bearing’ (BCA # MNJ471) and a ‘Brush set’ (Standard Motor Parts # CX8)

SMALL ALTERNATOR PARTS WILL BE: ‘Drive end’ bearing (BCA # 203SS) – ‘Commutator end’ bearing (BCA # MNJ471) Brush set (Standard Motor Parts #CX15)

Of course there are different part numbers by different manufactures. I use these numbers because I really try hard to stick with ‘Made in the USA’.

THE WORST part of this all is getting the pulley off the front. It’s a ‘press fit’ and they can be VERY stubborn sometimes. Especially if it hasn’t been removed in years. Don’t be surprised when you're cranking on the bolt of the puller, you think you’re going to break the tool and all of a sudden “KA-BANG!!” the pulley pops off. Once you’ve got the pulley off, the rest is pretty easy.

Now, remove the screws that hold the case halves together. Be kinda’ easy on these. Remove the screws (That were behind the pulley) that hold the retaining plate for the drive-end bearing. Now if your lucky the case halves will come apart easy. You may have to pry between them with a screwdriver. Even then, they should come apart fairly easy. You also will probably have to tap on the end of the shaft to pop loose the drive bearing from the case. It should come out pretty easy.




Now you've separated the case halves and pulled the rotor out. (You can take the brush assembly out first, if you wish, it’s only one screw, but it doesn’t really matter) Next you’ll want to remove the drive-end bearing. This is a ‘press fit’ also and you’ll need a small 2-jaw puller for this. It should come off fairly easy.







Now what you want to do is clean up the slip rings and drive shaft end.





I use emery cloth to clean these, although you can use Scotch-brite, a fine-grade sandpaper or steel wool. THE IMPORTANT thing is to remove the LEAST amount of metal as possible! Especially on the slip rings.







Remove the 3 nuts that connect the stator to the diodes. Be very careful not to damage the stator when handling it. When you’ve removed the nuts the stator should just lift out of the case. You may have to gently pry on the edge with a screwdriver.








Now, you’ll probably want to clean up the casing and remove the Commutator-end bearing (This will be just a cup with needle bearings)
You can tap out that bearing with a wood dowel and small hammer. Doesn’t matter which direction you go.





To clean up the case halves, you should remove the diodes and capacitor. It just makes it easier. PLUS you’ll want to clean all the electrical connections of these components.

Now, here’s the difference between the $100.00 rebuild and the $200.00 rebuild. The cheaper one, at wherever they rebuild them, will clean everything up, and replace the bearings and brushes. The expensive ones will also install new diodes and capacitor. You can do this too, but the diode trios aren’t cheap. Expect to pay about $25-30.00 for each. Capacitor is about $5.00 …. So you’re talking about another (About) $65.00 ….

Anyway, the diodes GENERALLY don’t go bad. THEY CAN, but in my experience, they’re pretty bullet-proof. (If you’ve ever had your electrical system, especially your headlights, have a kind of ‘strobe-light’ effect, THAT’S a bad diode(s) .. )
These are easy enough to check with a VOM. You should get full conductivity (Maybe a few ohms of resistance) in one direction and none in the other direction. In this particular rebuild, my diodes were fine, so I used the old ones. (Keep in mind, we’re trying to keep cost down as much as possible)
Capacitor is up to you. They’re cheap. These are pretty much bullet-proof also. Worse that could happen is ‘alternator-whine’ on your stereo.

OK! You’ve got everything apart and cleaned up. You’ve got your new parts ready to go.
All the electrical connections have been cleaned up and shiny-bright. You’ve cleaned up the rust on the screws, threads and heads. You’ve SAVED your old commutator end bearing, because you’ll need it. (Maybe you’ve gone over the casing halves with a wire cup brush and put in some elbow-grease to get the metal pretty shiny. This is what I did, and while it’s a lot of work, the results are pretty nice. You can also bead-blast the casing, but it doesn’t replace the elbow-grease. Should you choose to shine up the casing, I would recommend spraying a clear coat over it to keep it looking sharp…)

We’re ready to put this back together now!

I always start with the drive end, because I like to get the harder stuff out of the way first.
First thing is to get the drive bearing on. DO NOT FORGET to put your bearing retainer on first! Now, this is where you want to slip the old commutator bearing on the other end of the rotor shaft, just to protect it. My pictures show the assembly on the work bench, but I usually do this down on the concrete floor, because you’re gonna be banging on this. Stand your rotor shaft up on the commutator end, set the drive end bearing on the shaft, place a block of wood on top of that and tap on that to get the bearing going on the shaft. Once it’s flush with the end of the shaft, place an 11/16” Deep socket on the bearing and beat it on the rest of the way. It’ll go all the way down to the ‘step’ on the rotor shaft.







Now, take the front case half, place it over the drive bearing, again, use you deep socket over the shaft and hammer the casing over the outer race of the bearing..
Install the screws for the bearing retainer. Tighten the screws evenly a little at a time. Do NOT over tighten…







The rotor should turn freely with no funny noises.
Now we get to put the pulley back on. (Don’t be afraid! It came OFF hard, but goes back on fairly easy!)
Standing everything up on end again, place pulley on shaft, place wood block over pulley and start hammerin’ that sucker. You’re gonna need a pretty good sized hammer for this. I use a 3lb. small sledge.

NOTE: (If you have a buddy with a small press, this would be a good time to buy him a couple of beers and shoot the breeze, while you borrow his press.. ;^)

The pulley will only go on so far, so don’t over-do it. It should end up looking like this..











OK, spin everything around again. It should be nice and quiet with nothing scraping on anything…. You can take your old commutator bearing off the shaft and throw it away now.

Next, commutator bearing. Take your NEW bearing and seat it in the rear casing half. Place block of wood over it and tap it in till the end is flush with the casing. It should go in pretty easy.









Now, flip the rear case over and install the stator. Make sure you get all three lugs over the studs and install nuts. Be careful that you DON’T crank on these nuts to hard! SNUG is GOOD!





ALMOST DONE!!

Put the two casing halves together and install the screws. Get all the screws started and tighten slowly and evenly. When the screws are all tightened up (Again not TOO tight) the rotor should spin freely … Nothing scraping… No funny noises.

Last thing is to install the brushes. Install the assembly and install the screw that holds it in. Spin the rotor. The only thing you should hear is a slight ‘scraping’ noise from the brushes.




You’re DONE!! Install alt, and make sure everything is working as it should…



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Tankem
 
 Posted: 04-23-2008, 10:20 AM
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Post #2

Great job bherder!Another good write-up.Thanks.
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jdr1234
 
 Posted: 04-23-2008, 10:25 AM
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Post #3

EXCELLENT WRITE-UP!!!

Thanks for posting
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Megunticook
 
 Posted: 04-23-2008, 10:30 AM
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Post #4

Thanks for a great tutorial.

Hey, can we collect all these "how-to's" with photos and step-by-steps and put them in one easy-to-browse place online?

Is there a place on DT for this?

I could also host it on my website, where I posted my ignition switch how-to the other week.

I think it would really see a lot of use.
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bherder
 
 Posted: 04-23-2008, 07:07 PM
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Post #5

Thanks for a great tutorial.

Y'all are welcome!

Hey, can we collect all these "how-to's" with photos and step-by-steps and put them in one easy-to-browse place online?

Is there a place on DT for this?

Yeah, there is:
http://www.dodgetalk.com/forums/forumdisplay.php?f=379

Prob is, you gotta 'hunt' for it. You need to start at 'home' and go through 5-6 sub-folders. If you didn't know it was there, you'd never know it was there.

(ramchargercentral.com .... Has a 'How To' right on the home page. They however, are a LOT more vehicle-specific than dodgetalk.com ...)

I'd like to see a "How-To's and General Info" at the beginning of our forum, with sub-folders underneath THAT, but I don't run this site, it would take a bit of work on the webmaster's part, and... Sadly... Our old girls just probably are not popular enough for someone to put that much effort into it... (We ARE somewhat 'Dinosaurs' y'know.. And not 'popular' dinosaurs at that...)



I could also host it on my website, where I posted my ignition switch how-to the other week.

There is an IDEA! You'd have to make it available to anyone who Google'd your site though...
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DiverDwnPowrRam
 
 Posted: 04-23-2008, 10:13 PM
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Post #6

Great How To..I just printed them out and put them in my FSM. Could you say specifically where online you got all the parts?
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bherder
 
 Posted: 04-23-2008, 10:43 PM
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Post #7

Great How To..I just printed them out and put them in my FSM.

Wow! I'm honored! Thanks! (We may all die, but the MOPAR legacy will LIVE ON!!)

Could you say specifically where online you got all the parts?

I got the bearings from:
www.partsamerica.com

And the brushes from NAPA (Had to be ordered)

The 100+ amp parts are not all that common, (Except for the commutator bearing, which is the same for either) ... The 'small' alternator drive-end bearings, brushes, they should have in ANY parts store. And cheaper, too!
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pablo2377
 
 Posted: 04-26-2008, 09:48 AM
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Post #8

great job! it's been a while since auto shop in high school... allright a LONG while since shop class. These kind of tutorials are priceless to those of us who take pride, and find a great deal of satisfaction, in doing it ourseves.
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phildelfino
 
 Posted: 04-27-2008, 10:31 AM
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Post #9

VERY, VERY good stuff, thanks alot for this. It will be useful to everyone.
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Bruce88[81D150]
 
 Posted: 05-26-2008, 04:09 PM
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Post #10

great tutorial.

I don't think i have either of those alternators installed though, I have the smaller one in my toolbox. It still works fine, i just needed a bigger one for my radio stuff... and the lights still dim even though I also have a capacitor for the amp. I'll take a pic when I can. I think the one I have now is a GM 85amp alt. The little one I have is 63, according to a shop that put in the new one for me...err other one for me.
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bherder
 
 Posted: 05-26-2008, 10:52 PM
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Post #11

I don't think i have either of those alternators installed though, I have the smaller one in my toolbox.

Must be a heavy toolbox!

It still works fine, i just needed a bigger one for my radio stuff... and the lights still dim even though I also have a capacitor for the amp.

Heh heh .... One of those BIG-AZZED 1 farad caps? For the sub-woofer amp?
Yeah, still gotta have enough amps to power everything up though....



I'll take a pic when I can. I think the one I have now is a GM 85amp alt. The little one I have is 63, according to a shop that put in the new one for me...err other one for me.

Might wanna look into one of the foreign alts that Mopar started installing in... 90's?. Tons of amps without the size/bulk.... Built-in voltage regulator also....
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Bruce88[81D150]
 
 Posted: 05-27-2008, 12:07 PM
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Post #12

i think that's the kind i have, 85 amp. must be, my voltage regulator on the firewall isn't connected to anything. I'll have to look for one with even MORE power . The cap i have is 1/2 farad.

yea the box is pretty heavy, but it stays on the truck. (its the kind you put behind the cab in the bed.)
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