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Has anybody attempted to DIY their Alternator Rebuild?


2002Scoob

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Ya'll know me. 

 

I don't like to pay somebody to do something unless it's truly outside my skill or tool-set. 

 

My alternator has given up the ghost, but it is the original unit that came with the car, and honestly, the stickers look great and overall it's got a lovely patina that matches the motor beautifully. On-top of that, I don't really feel like throwing any more money than is necessary towards anything to do with internal combustion, since i'll be selling the whole drivetrain kit-and kaboodle this winter and embracing the electric future. 

 

I'm going to borrow my office's current meter to diagnose further, but I'm guessing that a diode has blown, so I'll be measuring across the posts to see if there's any AC current leaking into the system. 

 

Has anyone attempted their own rebuilds? if so, where'd you source your parts from? Stuff is looking a bit scarce here in Europe, but after diagnosis I'll take it to the local Bosch Shop and see what they can help me with. 

 

Cheers,

-J

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Other than diode and bearing replacement, there's not much else on an alternator that a DIYer can do--you can't rewind either the armature or the field coils (you couldn't on a generator either) without very specialized equipment.  

 

If you can find the correct value for the diodes, they're pretty easy to solder in place (get the polarity correct), and bearing rarely need replacement.  But that's about it...

 

mike

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'91 Brillantrot 318is sunroof-Georg Friederich 
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I've been looking at youtube videos of people rebuilding them, but haven't found anything 02 specific.

 

Some seem to have the diode/regulator as a separate part that bolts to the rear, and doesn't seem to require re-soldering. 

 

I guess I'll know more when I tear mine apart. Would love a quick-and-easy fix!

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1 hour ago, 2002Scoob said:

Some seem to have the diode/regulator as a separate part that bolts to the rear, and doesn't seem to require re-soldering

 

It's called a Diode plate, and depending on your alternator model, they may still be available through third parties. Of course, they are long NLA from BMW.

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Never had a Bosch alternator apart but have  troubleshot/ repaired many small aircraft alternators.

No real difference in design or construction, in fact  many were just relabeled auto alternators with proper certification (Translation: costs a lot more)

Are you sure its the alternator that's given up the ghost? Have you checked for current at the field wire (ignition on)? 

Easy check that could save you a lot of time,  eliminates the wiring and voltage reg as possible reasons for failure.

If you have current there maybe the brushes are bad.

Edited by tech71
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If it's the original alternator it's most likely worn brushes if they get to short they will bounce off the slip rings at higher RPM's causing low voltage at high RPM's if it was a diode your voltage would be low across the board.

Edited by Son of Marty
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I had a real hard time finding a source for all the parts needed to fully rebuild the alternator. What I ended up doing is I found a good deal on a rebuilt one by Remy with no core charge for like $50 on ebay. I just swapped all the new internals from the rebuilt one into the old housing.

 

My alternator had seemed to be fine and then suddenly stopped. When I opened it up it was real bad, pretty much every single piece of it had at least one thing wrong with it. Worn brushes, broken and frayed wires, etc.

 

if you do it like me and just swap everything it's really easy it doesn't even take an hour. If you replaced individual pieces and you know how to solder it should still be pretty easy. everything is just held together by a few nuts and bolts.

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9 hours ago, 2002Scoob said:

i'll be selling the whole drivetrain kit-and kaboodle this winter and embracing the electric future. 

 

That statement makes me sad...but I guess progress is not always warm and fuzzy.

 

As for DIY, it depends on the level of wear and how reliable you want it to be when repaired, IMO.  With regard to electrical and electronic parts I don't have enough knowledge to trust my work, especially if I'm doing long roadtrips and don't want to be stranded.

 

I have a lot of respect for auto-electric shops.  The good ones do a great job of electrical restorations.

I paid $200 for my last alternator rebuilds but that included bearings, diodes, brushes, plating, etc.

 

ALT5.jpg.a312a1f26fb01c34c9d613ec637fcacb.jpgALT4.thumb.jpg.11f0a161928b589731b0afd975d37cbc.jpgAlt1.jpg.046493fe7a679813a03ae7e9fc9d79e1.jpg

 

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40 minutes ago, Einspritz said:

 

https://www.aspwholesale.com/

 

https://store.alternatorparts.com

 

https://www.maniacelectricmotors.com/

 

That's enough for now.

 

 

 

Do you know if any of them sell stators? I looked but I couldn't find it, they don't have the most easily navigable websites.

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2 hours ago, PaulTWinterton said:

That statement makes me sad...but I guess progress is not always warm and fuzzy.

 

Don't be too sad, Paul. It's a solid little motor that'll hopefully serve well in someone's '02 that needs or wants it.  I'd love to hold onto it for the effort I put into it, but I need the funds and don't have the space. I am, however, working on turning the #'s matching block into an end-table :) 

 

2 hours ago, Einspritz said:

That's enough for now.

 

YES! I'll start diggin' in and see what I need and can get my grubby hands on. Dankeschön! 

 

4 hours ago, Son of Marty said:

If it's the original alternator it's most likely worn brushes if they get to short they will bounce off the slip rings at higher RPM's causing low voltage at high RPM's

 

This is the little tidbit I was hoping for, that makes perfect sense and perfectly describes my issue. If it's that simple, that would be an easy/cheap fix, if they're replaceable. 

 

I'm gunna crack it open tomorrow, or this weekend perhaps. I got suckered into a few rounds of Scotch with a friend after work, and didn't get a lick of diagnosis in, haha. 

Edited by 2002Scoob
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The word "rebuilt" is just totally misunderstood these days.

 

Yes, you can REPAIR a broken alternator.

 

REBUILDING one would involve completely stripping the coils off of it,

rewinding, relacquering, and so forth.

 

I've changed the $6 bearings and the $4.95 brushes before.

Even retrued the slip rings.  Diodes, nah, sourcing the parts 

was a pain before the internets, and parts alternators were

almost free.

 

They always work afterwards.

 

Now, voltage regulators, those little suckers...

 

t

320 alt in everything.  Well, or a Chevy Sprint...

 

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"I learn best through painful, expensive experience, so I feel like I've gotten my money's worth." MattL

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