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AZBMW Forums › General Forums › The Garage › Let's Talk Alternator Rebuilds
Let's Talk Alternator Rebuilds
DIY's and technical discussion
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Joined: Apr 02, 2012
Posts: 128

PostPosted: Mon Feb 22, 2016 4:57 pm
Post subject: Let's Talk Alternator Rebuilds


OK, I want to post this so that we can get some updated information out there. I'm very OCD and picky, so this will be long-winded. You've been warned.

I just finished rebuilding my alternator @ 135k miles and I must say that it was a frustrating process trying to find the items that I wanted to use (ie not garbage parts).

So, I am laying out my findings in hope of this helping people in the future.

First, the symptoms that I was getting included the following:

1) Flickering interior lights at idle.

2) Dimming DIC (dash display) with accessories on while driving, such as seat heaters and audio system up above 50% volume. With my stereo turned-up loud enough, every time the bass would hit on any genre of music I would get a significant dimming on the dash. Comparable to installing multiple amps and high-powered subwoofers without a capacitor or uprated charging system. I am on the stock audio system.

3) Surging/chugging at low speeds while trying to maintain a constant speed. Also induced difficulty shifting smoothly, similar to the kangaroo effect from the latest software for the E39 M5.

4) Chirping noise when cold, despite new belts. Also associated with this was an oddly worn rib in the drive belt. This was a combination of the armature making contact with the casing (chirping) and bearings that were trashcan material (worn belt rib).

5) Hum that seemed to come from the front-end sometimes and the rear-end others. This was due to the bearings in the alternator allowing the drive belt to pull the pulley ever so slightly and putting stress on the rollers inside. You could load and unload the car to test this.

6) Very light vibration felt at highway speeds.

With all of that said, even if I did not have an issue with the voltage regulator, that beast was getting changed as preventative maintenance while I was in there, regardless (I am happy because when I pulled my VR out the brushes were done). So, I set off on the quest to find the best parts. However, I couldn't believe that most people were just buying refurbished units with all low-spec'd Chinese parts in them and paying a pretty penny to do so. Some failed very quickly and others seemed to be OK; it was hit or miss.

I searched high and low for the bearings (which seemed to not be as easily available as they once were) and there was also uncertainty of what was in there from the factory and what the best bearings to use were. I will tell you what was in my particular unit and what I used.

Parts Used:

Voltage Regulator - Monark P/N 082 966 545
I got really lucky here. I happened to run across a company called Monark, out of Hamburg, after about 350 hours of searching everywhere for something other than a Transpo Voltage Regulator.

The guy I spoke with at Monark was very nice and extremely helpful. I communicated my desire to avoid a Chinese regulator and my disgust at the Bosch pricing for a new regulator. He did say that they had to move production to China a few years ago in order to stay competitive in the market (which makes sense) and assured me that their specifications are no different than when it was produced in Germany. He also disclosed that final QC is done in Hamburg. Spending some time in the manufacturing industry, myself, I have seen the yields that Chinese factories are capable of when given quality specs. So, I gave it a try and the part is performing well.

Now, the only rub is that there are really no distributors in the US for their BMW line. It took some doing to get the parts over to me but has proven to be worth it. They are currently looking for US distributors for the BMW line and it would be awesome if we could get a forum sponsor to pick them up. I am also testing their ignition coil in a friend's M5 (Mine are all fine) and it is promising.

I'm talking to local people that I am connected with, as well, to see if I can make a connection for them. I also think that they are willing to do a run for us if we can get an order above their minimum (which I believe is 400 Euro). Depending upon time constraints, I may be willing to front the money for this if there is enough interest.

Front Bearing - 17x52x17mm (B17-99) Monark P/N 083 955 012
This thing was a beast to find. I searched everywhere, high and low, and came up empty everywhere. I called companies all over the US and had trouble finding any major brands in this size. Really, the only place I found it was SmithCoElectric, so I bought it.

Interestingly enough, after speaking with Monark, they also had this part, so I got theirs too with the intent of using whichever one looked best. Well, when I pulled apart my alternator, the bearing I bought from SmithCoElectric was not the same as what I pulled out (despite being listed as "OE Bosch"). The Monark-supplied part was exactly the same, NTN with blue seals and matching part number, so I used that. Now, I am sure that the SmithCoElectric bearing is correct, but having the exact same bearing in front of me was enough for me to use it in my application (the original one lasted more than 15 years and 135k miles in Arizona so I am good with that).

Rear Bearing - 17x40x12mm (6203-2RS) Monark P/N 083 960 281
This bearing is considerably more common and easier to find. In this case, the SmithCoElectric-supplied bearing, Monark-supplied bearing and bearing pulled from my alternator were all the exact same. NTN unit with orange seals. Good deal.

DIY Resources:

I quite liked the episode of Wheeler Dealers where they rebuilt an E39 M5 alternator. Problem is, the links provided were all long dead, so here is an updated link to a working one (for now). It was valuable for me as a visual while working.

I also utilized this thread over at BF.C during the searching. It is still worth a read because they link you to a Land Rover document that has some good DIY info. It is not our exact alternator and I do not agree with everything said in there but it is a good resource nonetheless.

Lessons Learned and Tips/Tricks:

OK, so I did run into some "gotchas" and other issues that I'd like to outline below:

1) Autozone loaner tool program is great. I used this bearing puller and it worked flawlessly. I could not have done the job without it.

2) The Phillips screws on the front of the alternator, behind the pulley (that hold the plate to the casing), are a royal bi#*@. They were damn near welded in there. I was pre-warned about them and approached with care from the beginning but they still melted on me, just awful. If I were to do another then I'd just extract them straight-away and replace the screws (you can get them from Lowes/Home Depot for less than $0.45/ea).

2a) I used this to extract mine. It made short work of the screws. Saved my bacon. -

3) The casing that the crappy screws are in is pressed onto the front bearing. TAKE CARE WHEN TAPPING THIS OUT. If you do not have the alternator casing supported by a solid surface (I used two wood blocks to suspend it in the air without touching the guts of the unit) then you will be hammering the hell out of it until you ruin the pulley stud (ask me how I figured that one out. Stupid move). Luckily, I had a die kit and got it cleaned up. Use a rubber mallet. It should come out rather easily when supported properly.

4) The alternator can be removed easily enough by one person by wiggling everything out. It is a little tight for the power connection and VR plug but not impossible by any means. Just take care and be smart. I disconnected the power wire from the top of the motor to get extra slack (make sure the main battery cables are disconnected before even thinking about doing the job) and it worked fine. Once everything is disconnected then you can squeeze it out. Make sure that you remove the power steering pump from the bracket and support it with something (I used a spare jack stand) off to the side.

4a) Installation is awful by yourself. Ideally, you would want someone to help hold the alternator while you get it started back into the very tight mount. I was on my back, by myself, after going a little hard in the gym earlier in the day so I was burning all the way down my forearms and swearing like crazy. I felt uncomfortable putting too much *** hair on the alternator because I could hear the jack stands making a bit of noise and that's never good (alternator installs by putting pressure toward the passenger side).

Summary/Cliff Notes:

1) Monark is awesome. They had everything I needed for this job (including the proper bearings) and were great to deal with.

2) Get a friend to help

3) Rubber Mallet

4) 3-Jaw Puller

5) Alternator casing screws are jerks


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Posts: 128

PostPosted: Sat Jul 16, 2016 2:19 pm
Post subject: Re: Let's Talk Alternator Rebuilds

Well, it has been about 6 months and 10k miles since I did this rebuild and I thought that it would be appropriate to give an update for anyone looking through this thread.

I am happy to say that the car has been great and has not skipped a beat. It still performs exactly as it did right after I did the rebuild (which is a pathetic thing to be celebrating, if you ask me... something that is doing what it is supposed to do, but that is our day and age). The alternator is quiet and I don't have any dimming or pulsing at idle nor under high load.

I think that I can safely say this package is the way to go when rebuilding. I am very happy.

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