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X5 Voltage Regulator 220 AMP

16K views 31 replies 10 participants last post by  Westlotorn 
#1 ·
I have a 2008 X5 with adaptive drive so requires 220AMP alternator.

Cheapest I can find online is around $700. Was wondering If I should get a voltage regular (~150) since I'm pretty sure the issue is with the regulator and not the alternator itself.

Anyone ever tried replacing just the voltage regulator?

Issue I'm having is this: When I start the car, sometimes it takes around of 5 to 10 minutes for the alternator to kick in and start charging. So when I do short drives, the battery gradually dies and I need to jump start the car. Appears to be worse during warm weather. Weird.
 
#2 ·
Given that price difference, and assuming you are doing your own labor, I would give it a shot....

Can't tell you if those symptoms match a 'regulator issue', but it IS my iunderstadning that many (most?) alternator failures are in fact regulator failures.

GL
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#3 ·
In the BMW IBS electrical system, the alternator output voltage is controlled by variable excitation (current to the rotor through the slip rings) from the ECU, and the component being called "voltage regulator" is the output rectifier stack.
 
#4 ·
Sounds like you are saying replacing voltage regulator may not solve my issue then?

So, this has being going on for about a year ... summer time when I start the car cold in the morning, everything looks 'ok' (digital volt meter in cigarette lighter i installed showes over 13v). Around lunch time when I start the car again, voltage shows 11.x ... gradually drops to around 10 or 9 and all of a sudden (in about 5 to 10 minutes) it jumps to 13v+ and it stays like that until I restart the car again but then it may start with 13v+ again or 11.x and later jump to 13v. As long as I turn the car off while it was running at 13v+, I don't have trouble starting the car again.

Now, last few months when weather was a little colder (may be other variables i don't know but weather is the only variable I can think of), I almost never saw voltage drop below 13v+ so all had been well up until a few days ago when the outside temp was around 70+. What happened here was a little different and had never happened before: When I started the car it started with 13v+ and after few minutes, I noticed voltage started to drop (while driving -- again never happened before) ... it continually dropped passed 10v, 9v, 8v .... when it got down to 6v the car pretty much stop responding so I turned it off and as expected I was not able to start it up until I jump started it about 30 minutes after I turned it off and now voltage is back up to 13v+ again and was able to drive around a little. At this point, not driving the car again afraid it would go dead again while driving and kind of assumed replacing alternator or voltage regulator would solve the problem.

I guess, if I had 180amp alternator, I would just pay $200, replace alternator and see what happened but with 220amp alternator and $700 cost for parts, I was thinking I should do a little more looking into this so appreciate all the help/comments.
 
#5 ·
CR is cheap enough so I don't think you have anything to lose. Which engine do you have? On N62 4.8i it;s fairly straight forward it seems, at least on the E63.
 
#6 ·
For what it's worth (not much, I'm sure), I replaced my voltage regulator about a year ago when I hit the 100,000 mile mark. I did it because both of my son's cars had their voltage regulators die at about that time (approx. 140K on an e53, and around 200k on Mercedes ML320). With my son's cars, the carbon brushes were worn out, and a new voltage regulator fixed things right up. Of course, there are bearings in the alternator, and slip ring conductors that can also get worn out, but (as noted by ard) my understanding is that many/most alternator failures can be fixed with a voltage regulator. Just as you have noted, a voltage regulator is much cheaper than a whole 220 amp alternator - so I did it as (moderately) cheap preventative maintenance.

It was a pretty easy DIY. Hope that helps.
 
#7 ·
..........With my son's cars, the carbon brushes were worn out, and a new voltage regulator fixed things right up. Of course, there are bearings in the alternator, and slip ring conductors that can also get worn out, but (as noted by ard) my understanding is that many/most alternator failures can be fixed with a voltage regulator.........
I've never had a bad electronic regulator. In my experience, worn brushes are the problem. In 45 years of wrenching and 35 years of Bimmer ownership, I've only had (1) case where replacing regulator brushes wouldn't fix the charging problem. That standout, my daughter's E39 w/158k, had an open circuit in the rotor, preventing creation of the excitation field. If you can change the regulator, changing the brushes isn't that much more effort, provided you can solder. Bosch & Valeo brushes are available on ebay.

..........the alternator output voltage is controlled by variable excitation (current to the rotor through the slip rings) from the ECU........
I don't think the DME provides the excitation current directly. The schematic I recall seeing showed the DME sending a BSD signal to the alternator. This seems more like a "remote setpoint" capability. It would allow the DME to command a change in alternator output to achieve "efficient dynamics". This more complex regulator might explain why regulators have gotten so expensive.
 
#8 ·
The engine is N53 I think? X5 2008 3.0i. Electronic suspension.

As long as I won't need special tools, I shouldn't have problem with taking it apart and do whatever soldering needed. Are the brushes somewhat universal? With this rare 220amp alternator not sure how much trouble it would be find the right brushes if they are specific to my alternator.
 
#9 · (Edited)
pshovest is absolutely correct. And in fact I have soldered in replacement brushes for a couple of the family cars along the way.

This YouTube video

The above YouTube video gives a great discussion/demonstration of the repair. And that same fellow has another couple of videos demonstrating how to replace the slip rings and bearings if you want to go that far (which I didn't). Anyway, I think it is nice to support such videos/efforts, so I bought the valeo brush set from his ebay site (the link is here to the brush set [14.5x6.3x4.5] I used on my 220 amp valeo alternator in a 2010 35d). So if you trust your soldering, the cost for this is way less than the voltage regulator, and way, way less than the whole alternator! As I recall it took about 7-10 days for the brushes to arrive from Ireland.

Good luck.
 
#20 ·
That's a tough one. I recall another poster reporting a long time for alt to get to 14v. He replaced the entire alternator. If brush length looks OK then I would suspect regulator issue. But brush length affects contact pressure on slip rings, shorter brushes means less pressure. I'd sure like to see the effect of new longer brushes but replacing regulator will avoid a potential 2nd R&R of alternator.
 
#21 ·
I cleaned brushes/slip rings and put them back (real easy to get both alternator and voltage regulator out - less than 10 minutes). Seemed like brushes had decent contact with the slip rings but yes I was thinking the same thing maybe they needed to be tighter. Anyways, I put the alternator back and still had the same issue.

Was thinking going with voltage regulator to rule out both at one time. Looks like I can get voltage regulator for my 220 amp at around $60 and should arrive in 2 days. Brushes would have run me around $20 and take over a week to arrive. But, yes, out of curiosity I would have liked to have just replaced brushes first.

Any thoughts on how I would slip the new regulator in onto the slip rings without taking the cap off? Followed the youtube video recommendation for taking the cap off and mine didn't come out that cleanly. I don't suppose I would need to take the cap off of the new voltage regulator.
 
#22 ·
I think the new regulator will ship with a cap/clip/pin that keeps the brushes retracted until it's screwed in place. You then remove the cap/clip/pin and brushes release and contact the slip ring. BTW, how many miles on the alternator? How are you measuring alternator output....at the cig lighter on in the cluster thru the OBC?
 
#23 ·
Thanks. Ordered regulator and should arrive Tuesday.

I am beginning to feel confident the issue is temperature related. When I put the alternator back (old one with brushes that I only cleaned) it started up fine with 13.6v. Obviously cold start since car had been sitting for days. Now, when I drove around for a little while and I turned it off and turned back on, alternator didn't kick in. Voltage reading was around 11v. I turned car off and let it sit. Started it up cold next morning and right away jumped to 13.6v.

I suppose it is possible that brushes are worn and when the alternator/regulator gets hot, the brush springs lose tension and don't make full/tight contact? Just a thought.

Oh, and using digital volt meter via cig lighter.
 
#26 ·
I did see a few 220amp alternators around $230 that from front and side look exactly what I have but the back side is not the same. There is a single pin connector that doesn't seem like goes anywhere on my alternator. Ones you are referring to the connector looks a little different and is at a different angle. Ones that look exactly like mine are around $700. Not sure if those $230 ones would work on my car.
 
#25 · (Edited)
Also keep in mind that these cars MAY be doing things load management behind the scenes as the engine warms up. For example it may reduce the load on the alt, basically require little output, until the engine is up to temperature- THEN could load the alt. This would reduce pollution from loading a motor as it is warming up. (Not much, but every bit counts...) it might just LOOK temp related..


Not sure, just wondering out loud
 
#28 · (Edited)
This is a total shot in the dark, but in case things are not fixed with the voltage regulator, I just read about the balance shaft pulley in a bmw diesel deteriorating and causing stiff steering and charging issues due to drive belt slippage. The link is here:https://bmwtechnician.com/2017/03/19/diesel-pulley/ I suppose you would use a mirror to look into the inner portion of the balance pulley and see if there are any signs of deterioration. Something to think about, anyway.

With regard to the brushes and cap of the new voltage regulator - when it comes out of the box the black dust cap will be raised up halfway. The inside of the cap pushes back the spring loaded bushes to allow easy mounting of the voltage regulator. Once it is mounted, you push the dust cap all the way down. You should hear and feel a "pop" or "snap" as the brushes come into alignment with some cut out tabs in the dust cap and the brushes spring out into position. I don't know if my explanation makes sense, but hopefully it will after you see the voltage regulator and dust cap.

Good luck.
 
#29 ·
Just replaced the voltage regulator ($59). Will need a day or two to really find out if my problem is fixed but I like what I see so far since this new regulator shows voltage around 14v (goes up to 14.4v) while my old one was maximum around 13.4v when it worked.

Something else may be worthy of noting: With my old regulator when I started the car up, voltage either jumped to 13.4v within less than a second or so during cold starts or took up to 10+ minutes during warm restarts. Now, with this new regulator, when I start the car up, voltage remains around 11v initially and takes about 4 to 5 seconds to jump up to 14v. I'm sure not an issue.
 
#32 ·
I know this is an old post but I have had the exact issue for months now with my 2008 BMW X5 4.8L. 11.6V on start up, anywhere from 1 - 10 minutes later the alternator starts working and voltage jumps to 14+ Volts. No matter how much I load the electrical system it will stay at 14V once it kicks in. Problem is the low voltage sometimes will cause check engine light to come on which do not clear unless I use my scan tool. Alternator is still quiet so I am thinking of replacing the voltage regulator and roll the dice. Looking at this alternator in the 4.8 it is buried in a hard to reach place down low driver side. Not looking forward to this job. Several years ago I had to replace the high pressure oil cooler seals behind the alternator but I guess I am getting old. I do not remember how I removed the alternator. Glad this post was available to give me some direction for this repair.
Just removed and cleaned the cam solenoids yesterday so I was looking at the alternator project.
Mark
 
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