# Got a dead Alternator, can I replace the voltage regulator and save some $$$?



## MEDEL514 (Jan 12, 2002)

I have a 2001 Audi A3 1.8T Quattro and the car died on me the other night, first the radio cut out, the interior lights went dim, headlights dimmed, and it eventually died. The battery tested good, so I believe it was the alternator that went out. 

My question is can just the alternator's voltage regulator be replaced on the back of the alternator? I used to do this with my Mk2's and 3's, seems that the voltage regulator on those would go out before the actual alternator did. It was a $14 fix vs. a new ~$150 alternator. I'm hoping that maybe I can do the same for these 1.8t alternators and avoid a new ~$250 alternator! Anyone ever do this on these 1.8t's? I've searched these forums, and looked for just the voltage regulator on parts websites with no luck, so I'm hoping someone on here has any insight.

Also, what readings should I be getting from a working alternator? I don't have a Bently for this car. Any help would be appreciated! Thanks!


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## MEDEL514 (Jan 12, 2002)

I'm slowly starting to come across some info on the voltage regulator via google search. But damn, are these regulators expencive? like $140? I may as well buy a new Alternator and be done with it!


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## groggory (Apr 21, 2003)

You don't know what the issue is with the old alternator.

I would leave the rebuilding to someone who knows how to fully inspect it.

Just buy a new/rebuilt unit. Get the 120A from the VR6 if you have a choice.


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## MEDEL514 (Jan 12, 2002)

I finished testing and re-charging the car's battery yesterday, installed it, and did a little further trouble shooting. With the car running, the voltage readings are 12.2V, and drops down to 11.8V when I apply more of a load (lights, radio, etc.) Searching through the forums I'm supposed to get 14.7V with a good charging system. So this tells me that the alternator is not working properly.

Now the biggest reason I am pushing for a voltage regulator change is because a new Alternator from the dealer is ~€500 (Euros, about $625, and about $300 online), and a new voltage regulator is €58 (about $72). It's a no braininer that I would try to avoid a costly alternator swap if I didn't need one. So I got the voltage regulator off of the old alternator and heres a pic of the parts:










Take a look at the shaft, would you guys say that it's worn out of limits? or does it still have some miles left on it?









And here are the brushes from the voltage regulator. You can see that the inner brush (closest to the core) has significant wear over the outer brush. 









So what do you think? I knida still want to press on and swap the voltage regulator unless you guys can see any reason why it would be better for me to just buy a new alternator. Any help is greatly appreciated! Thanks!


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## groggory (Apr 21, 2003)

I would say the brush is your most likely culprit.

I don't know the test procedure for the vw alternator diodes....but from what I understand, the diodes don't go bad too often.


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## 18T_BT (Sep 15, 2005)

I was able to find a 120a at my local salvage yard when mine pooped on me, it was around 50 bux, so much cheaper then the dealer or replacing the brushes or diodes. I donated my old one to a local shop, so they can have a core/spare.


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## MEDEL514 (Jan 12, 2002)

Just an update, I replaced the voltage regulator and it solved my charging problem, and saved me a ton of cash! Sweetness!!


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## groggory (Apr 21, 2003)

MEDEL514 said:


> Just an update, I replaced the voltage regulator and it solved my charging problem, and saved me a ton of cash! Sweetness!!


 Where'd you get the new voltage regulator? Part Number? Supplier?


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## MEDEL514 (Jan 12, 2002)

I got the voltage regulator from the German Audi dealer for 46 Euros. I can't remember the part number, he looked it up from his parts catalog. I'll have to check again when I get home.


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## groggory (Apr 21, 2003)

MEDEL514 said:


> I got the voltage regulator from the German Audi dealer for 46 Euros. I can't remember the part number, he looked it up from his parts catalog. I'll have to check again when I get home.


 Please do. Sounds like an awesome find that could save people some good cash


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## MEDEL514 (Jan 12, 2002)

OK here's what I got: the P/N from my alternator is 028 903 028 E 

The "BOSCH part number" stamped on the back of my voltage regulator was: F 00M 145 225. The part number for the voltage regulator in the Audi parts system is 038 903 803 EX which was replaced by 06F 903 803. I paid 46 Euros for the voltage regulator from the dealer, not bad for an OEM part! 

I also broke the black two pin connector on the back of the alternator because most of the plastic parts on the 10 year old motor become brittle over time. That P/N is: 1J0 973 772 

Again, please verify parts for your vehicle with a dealership or another authorized parts dealer. I hope this thread helps save others some time and money in the future! :thumbup::beer::thumbup:


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## groggory (Apr 21, 2003)

Thanks. 

Added to FAQ


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## SCK (Jul 13, 2000)

*Thanks!*

I had a similar problem, and I'm glad to come across this thread! Turns out voltage regulator brush worn out for me as well (not surprised for a 13 yrs old car), save me tons of $$. Took me a while to get the part thou, had a quick chat with the parts manager, no body stock just the regulator since service department always change the whole thing to save technician time.


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## TacoVW (Aug 28, 2013)

Just changed the regulator on my alt with a $13 incl. shipping chinese one... let's see how long it holds up. :laugh:

I'm gonna try and drill out the epoxy on the stock one, and swap brushes.


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## MEDEL514 (Jan 12, 2002)

TacoVW said:


> Just changed the regulator on my alt with a $13 incl. shipping chinese one... let's see how long it holds up. :laugh:
> 
> I'm gonna try and drill out the epoxy on the stock one, and swap brushes.


About 10 years ago in Tacoma WA, there was a VW parts store that would stock replacement parts, and rebuild parts like the Alt brushes. I wish there were more places like that nowadays for crafty guys like us


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## groggory (Apr 21, 2003)

MEDEL514 said:


> OK here's what I got: the P/N from my alternator is 028 903 028 E
> 
> The "BOSCH part number" stamped on the back of my voltage regulator was: F 00M 145 225. The part number for the voltage regulator in the Audi parts system is 038 903 803 EX which was replaced by 06F 903 803. I paid 46 Euros for the voltage regulator from the dealer, not bad for an OEM part!
> 
> ...


Just ordered that voltage regulator on amazon (~$24). I had my battery tested by AAA and the tester showed excessive ripple from the alternator. That tells me the regulator is probably on its way out and isn't doing my car any favors. I'm going to try to rebuild my alternator. I'll keep you guys posted.


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## Chickenman35 (Jul 28, 2006)

groggory said:


> Just ordered that voltage regulator on amazon (~$24). I had my battery tested by AAA and the tester showed excessive ripple from the alternator. That tells me the regulator is probably on its way out and isn't doing my car any favors. I'm going to try to rebuild my alternator. I'll keep you guys posted.


Excessive ripple may be the Diode pack... not the Voltage Regulator. But give it a go and post back with results.

BTW, I always like rebuilding OEM alternators rather than buying a rebuilt. You can save a lot of money and quite frankly, do a better job than some of the rebuilt junk on the market. Even Bosch reman products aren't as good as they used to be. 

Rock Auto usually carries a large assortment of hard to find Alternator and Starter parts. It's usually a small part that fails ( Brushes, V/Reg or bearings ) and you can take your time and do a quality install.

IE: With new sealed bearings, always pop the seal off and repack the bearings with synthetic grease. New bearings these days never have enough grease. You can clean and polish the commutator with some Crocus cloth ( Machinist cloth - 2,000 to 4,000 grit ) . The OEM Stator and armature should last the lifetime of the car.


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## groggory (Apr 21, 2003)

Chickenman35 said:


> Excessive ripple may be the Diode pack... not the Voltage Regulator. But give it a go and post back with results.
> 
> BTW, I always like rebuilding OEM alternators rather than buying a rebuilt. You can save a lot of money and quite frankly, do a better job than some of the rebuilt junk on the market. Even Bosch reman products aren't as good as they used to be.
> 
> ...


I thought the diode pack was inside that voltage regulator module. I think you did a writeup on this awhile back. Do you have part numbers or any tips for me on parts?

I'll document the rebuild process once I start tearing into it.


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## Chickenman35 (Jul 28, 2006)

groggory said:


> I thought the diode pack was inside that voltage regulator module. I think you did a writeup on this awhile back. Do you have part numbers or any tips for me on parts?
> 
> I'll document the rebuild process once I start tearing into it.


Pretty sure the Diode Pack is separate from V/Reg. Diode packs are usually pretty big and have very large heat sinks. Do you have a Valeo or Bosch Alt? Alt model number? 

You're probably going to find that your Diode Pack looks something like this. Note: Generic picture:










Bad news: RA doesn't have any cheap prices on the VW/Audi V/Regs. Good news: Lots of Alternator and Starter parts available for my 1976 280Z and other early Datsuns dirt cheap!!


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