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Voltage Regulator issue (Bosch Alternator)

5K views 26 replies 7 participants last post by  yeldogt 
#1 ·
Had a weird issues this week with my w210 2001 E430 4Matic and thought I'd shed some information is someone finds themselves in the same boat.

Visit Workshop message lit up on the instrument cluster Battery/Alternator.
Checked voltage with car running at first 14.5~ but the next day 11.65~, car off 12.5~.
With car off interior lights would be dim, with car running the interior lights would get brighter if I rev the engine.
Checked battery (9 years old) and tested good with an advance auto parts load tester.
Removed the alternator, took it two different advance auto parts, ran total of 4 test, showed good each time.

This is when I got frustrated and decided to take the alternator apart and see if I can spot anything unusual. Didn't get very far, as soon as I removed the voltage regulator I noticed that the lower brush (if the alt is sitting on a bench pulley side down) is much shorter than the upper one. I put it back in place and noticed that it was barely making a connection. Figured I have nothing to lose I stretched the spring that it is attached to by gently pulling on the brush with some pliers (maybe 2mm). Put the voltage regulator back in place and observed that both the brushes are now making good contact. Again, thinking I have nothing to lose I installed the alternator and fired it up, no more error message and charging like it should so far (50~miles). Got a new voltage regulator on order to keep handy for when this one quits again as this is surely only a temporary fix.

Side note, everything I read about removing the alternator on the E430 mentions removing the fan clutch, fan, shroud. Not having a fan clutch removal tool, I was able to remove just the fan from the clutch along with the shroud. I gained a little bit of much needed clearance by unbolting the radiator tie support and just pushing the radiator and the support forward about an inch while I was unbolting the fan from the clutch. The rest was the same as all these wonderful write ups from other members.

Thanks to all the wonderful members who post all this helpful info, hope I end up helping someone as well.
 
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#2 ·
Depends on electricity usage, the alternator brushes wear out in 150-200k miles range.
Before they die completely, they will spark for some time - giving inconsistent performance.
I've been advising for VR regulator replacement on aging cars, but that is one of the most neglected items.
I bought 2008 model, but with 163k already, the VR was the first thing to replace.
On newer cars VR retails $140, whole alternator goes into 4-digits.
 
#3 ·
Ouch that's steep!

My E430 just hit 217K, I guess I should be happy with as long as the VR did last, and it definitely looks like it is the original one.
We have 4 MBs in the family, including a 2006 E320 CDI with 230K on it, I have a feeling I'll get good at this procedure.
 
#6 ·
Even $140 retail for VR might sound steep, when you put it on planed replacement, you will find it at internet dealer for $60.
No matter how much you pay for VR, the other alternative W210 owners occasionally posted on the forum is
-$300-500 towing bill
-$800 for new alternator (dealers don't do VR)
-$450 labor
-$300-600 for stuff dealer will talk you into replacing like new belt, idler pulley, water pump, MM and such.
-add car rental, spoiled food you had in the trunk, lost day of work and more.
So the few dollars and 1-2 hr spend on replacement at 150k miles mark can save you quite a bit not only in dollars, but in frustration as well.
 
#12 ·
For what it's worth, I replaced my VR last year (at about 200K miles - it was the original) and one of the brushes was quite a bit more worn than the other. No play in the pulley either.

And, I was able to replace it without removing the alternator from the car. A bit tight working from under the car but not too bad.

Fred
 
#7 ·
Zabac dont bin the old one .I picked up a set of new carbon brushes from ebay in the uk ..If you look you will find a electronic company that will sell them in the usa .Then remove the old brushes and install new ones . I did purchase a new regulator .Thats sill in the box ,,and as been for three years now.
 
#14 ·
An alternator installed in the car with the serpentine belt tension on the pulley can behave quite differently than the same alternator on the bench. So I do not think much of bench-top alternator testing. It should be done in the car under full load (whatever the rating of the alternator is) with no other consumers on (except the ignition power) at 2000 to 2200 engine rpm. So I wonder how they tested your alternator and said it was OK?
 
#16 ·
Alternators, or at least the VR can be tricky.
I had one rebuild alternator on Ford showing occasional red light short time after installation.
Yet week later it passed bench test. Took it like 6 months of acting before it died permanently and I could proceed with warranty.
Than wear out brushes can act/spark for quite some time. Occasionally when the brush hangs- tapping the alternator will give it necessary movement.
Short brush might hang open in one alternator position and work in other position.
Still why so much fuss on relatively cheap part, that has to go at some time?
I was replacing VR without removing alternator on I6 engines just fine. Took ratcheting Allen bit for close spaces, but quite doable.
On V6 diesel I would have to take something apart to remove alternator from the engine, but after taking it off the bracket, I was able to turn it in the engine bay to make back plate facing up, what made for easy VR replacement.
 
#22 ·
Almost exactly ten years ago, I built this alternator load test bench for a quick test of an alternator rebuild I'd done. I think I threw it together in about two hours. The drive motor is from my old Craftsman table saw, as is the belt.



Nissan diesel alternators of the 80s have a vane-type vacuum pump bolted to the rear of the alternator housing, and a special extended rotor shaft to drive it, so you don't usually get off easy when trying to buy a replacement or rebuilt unit: you either fix it yourself or have your core rebuilt.

As it turned out, I ended up rebuilding several for my forum members etc. Diodes were especially fragile on those old LR-series Hitachis.

------------

I picked up a new Chinese 150A alternator with overrun pulley that's supposed to be a bolt-in on my E300, and I thought I'd give it a run and see what I think of it. Haven't gotten around to swapping it out yet, and of course I'll be reconditioning the OEM unit and keeping it around.

I don't normally leap to Chinese aftermarket stuff, but this one had a good rep. I want to see for myself, and the price was quite reasonable.
 
#23 · (Edited)
FYI -- I purchased the correct Valeo OE alternator for my 02 E320 4matic last August for just under $250. Do the 430's use the same MB part number?

Rockauto had the best price at the time. The Valeo part number is #439307 ... it's not always listed in the aftermarket by the car's application.

That's for a new unit -- not rebuilt .. or from China. I called Valeo direct and got the internal part number.
 
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