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DIY: voltage regulator

320K views 168 replies 84 participants last post by  Fly Navy 
#1 · (Edited by Moderator)
Hello everyone,

I saved so much money working on my BMW and all thanks to e46fantatics! Thank you everyone for posting! I feel that I have to give something back to the community. So here is my first diy guide.

I searched this site, google, could not find how to change voltage regulator and brushes on e46. Decided to do it myself.

Initial problem was that alternator would give only ~10.3V if I had my lights and AC on. That drained my new battery. As my car is 2001 (06/2000 production), I decided that it was either brushes or voltage regulator. Ordered Voltage regulator (it comes with brushes) from pelicanparts, it is $53 (compared to $212+shipping on re manufactured Bosch alternator).

There is a good guide how to replace the alternator


here,


so I won't repeat it. When you have your alternator out, there is a plastic back plate. You have to remove one screw (#3 in picture and two nuts (#1 an #2). #1 is under this rubbery plastic cover, use screw driver to pry it out.

- The nut holding down the positive cable is 17mm
- #3 is a Philips screw
- #1 and 2 are 15mm nuts (deep wall socket is most likely needed)





After you remove the cover, you should find ..... this :tsk:




I found all sort of stuff - leaves, paper, cigarette butts, you name it. The voltage regulator is connected with 3 screws and slides out after, no clips.
My old brushes were worn, but not to the extent that alternator would not work, one was shorter than the other one. Go figure...





The whole process takes about 10-15 minutes (after you have alternator out). It is cheaper that buying refurbished alternator and it is way cheaper than taking to the dealership. If you alternator does not make any noises (ball bearings) changing just the regulator will save you lots of money. I believe it is easier to do this than remove the pulley while switching alternators... After I changed the regulator, with long beams on, AC on it runs 13.6V to my battery, I believe that is within specs of 13.5 -14.5V. Maybe on the lower side, but hey, its not 10.3V like before.

I hope that helps someone.

Part number from pelikan $53 12-31-7-559-183-M14 link
 
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#7 ·
I got this question:
Saw that you pulled your alternator. Is there any way to tell from the top if it's a Bosch or Valeo?

The answer:
Yes, you can, but you will need a mirror and a light. There is a sticker on the black plastic back plate (you can see that in the first picture - it looks like some bar code). It is faint on my alternator, but it is readable. I would suggest removing air filter housing (easy - 2 10mm bolts). You might be able to see even without taking it out, but it will be very very hard to get down to alternator ....
 
#66 ·
determining which alt you have



I'm having voltage issues in my 6/03 ZHP. After reading this thread and another (http://forum.e46fanatics.com/showthread.php?t=792768), I figure the likely culprit is the VR.

In terms of preparation, I wanted to know which alternator I have so that I can buy the correct VR, without removing either one. I used a telescoping mirror and shot the following photo of the sticker on the back of the alternator (VR cover?). The only thing I removed is the air filter box.

Ran a search on the number in the bottom of the pic (0124515105) and it turns out that's the Bosch part number for the 120A alternator.

Note to those who like me who cannot see this label without a mirror: I shot the pic on iPhone, flash off, then used Preview on a Mac (not iPhoto) to make a mirror image of the photo so that I could read the numbers more easily.
 

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#13 ·
I just got done putting a new voltage regulator on the Bosch alternator for my 2002 330ci and it works great! It's putting out 14.3V! I've got 67K on the car and the bearing and the rest of the alternator are in good shape. I did use a wire brush to clean any corrosion on the copper wiring found under the cover. I would highly recommend this repair. Also, a lot of the larger auto parts stores will do a free alternator and battery test.
http://www.autozone.com/in_our_stores/free_testing.htm
Thanks for the post! I saved over $700.00.:thumbsup:
 
#15 · (Edited)
Also, a lot of the larger auto parts stores will do a free alternator and battery test.
http://www.autozone.com/in_our_stores/free_testing.htm
I don't know about everyone else, but when my charging light went off the other day, this was the first thing I did, pull the alt and get it load tested. My alternator tested good at both autozone and o'reilly, so I slapped it back in the car thinking it was a different problem. After pouring over these forums and tracing that green wire off the alternator (not the one that goes to the light) I went with my gut and bought a new alternator anyways (after unhooking the lug and checking voltage on my own). Now the car is fixed. The testing setup at both parts stores gave a false reading.

As a side note, the alternator at O'reilly was only $200 + core with a lifetime warranty. Now I hate having a "china" sticker on my car as much as the next guy, but if you're frugal, I figured I'd throw that price out there.

Do you think you could have replaced the voltage regulator without removing the alternator? Is there enough clearance to remove the air-intake assembly (screwed to the alternator) and wiggle the regulator into place?
As for that, I doubt it. It might be possible, but with enough wiggle the alternator came out of my car with no hassle at all. I'd say just pull the alternator and swap the regulator, it would be easier than fuggering with the low clearances behind it.
 
#19 · (Edited)
Hi Everyone, I own a 2003 E46 318i (N42 valvetronic) with 125 000 km.

I hope someone could help me a bit. I have been having this problem for the last 6 months or so.
My alternator lights comes on for a second or so togther with the a drop in revs and a jerk.
I have replaced my battery, still the problem exists.
I have recently reconditioned my alternator, so new Regulator, new pulley, new bearings. But still the problem exists.
But I must say the IDLE is alot smoother now.

I also had my car hooked up for Diagnostics , it states that Cylinders 1 and 2 are running at 60% effeciency.
So now I'm not sure if the engine is cutting off for some other reason which causes the alternator to stop spinning
for a short while which lights up the alternator light.

Or the alternator core is dying causing the alternator to behave erratically.

Currently on idle my alternator pushes out 14,3v but after driving around a while it drops to 13,3v.
And the problem always happens after driving around for 20 minutes or so when the engine is hot.
So it's possible the core is dying once it gets hot.

But the strange part is that after it jerks and the light come on for that second, then on most occassions it's fine for th rest of the journey.
Several times it stwitched off at the traffic lights. But starts up fine again.

It seems like if the REVs are high enough it does switch off but kicks itself into life but with REVS low like at the traffic lights it can't kick itself, so it stalls.

Does any of this make sense. I really don't want to spend more money on a new alternator if it doesn't solve the problem.

Any help would be appreciated greatly.

Can the alternator die just for a second or so, just enough to stop energy to the plugs which causes the jerk or

is it possible the engine cylinders 1 or 2 cutoff due to bad plug etc, causing a stall or jerk which also causes the alternator light to flash ?

Does the voltage drop on the alternators when it gets hot ?
How low can the voltage go before it causes problems ?

You would think that if the alternator voltage drops below a certain point for a second or so that the battery could provide the energy required without the engine missing a beat.
 
#24 · (Edited)
You would think that if the alternator voltage drops below a certain point for a second or so that the battery could provide the energy required without the engine missing a beat.
I was able to hobble about 20 miles with no alternator when mine went out, I even had my headlights on (it was night time). The motor was spinning with no troubles. When I got home the lights barely lit 3 ft in front of the car, but the motor was still running fine.

I think your diagnosis of a busted core makes sense, but why it would intermittently cut on and off with a new regulator and brushes befuddles me. Is the low voltage reading of 13.3 still higher than the battery alone?

What I did to diagnose my troubles (after two false bench tests at the discount shops) was to totally disconnect the alternator and let the car run off of the battery (probably not a good idea, but I was frustrated) and check the raw voltage coming out of the alternator. If you could replicate the 60% problem this way, it would prove that there is something other than the alternator with a problem.

The 60% 1-2 cylinder efficiency thing may be a different problem altoghether, and if the problems ARE related in some way, its new to me, and someone that knows more about straight BMW's should be asked.

I'm still pretty new to this whole BMW thing....

One last thing-- if the block-frame ground strap is having troubles, cranking might become a problem too.
 
#21 · (Edited)
Hi Lbert,

Thanks for the info. So let me understand this better.

There is no physical ground connection between the alternator and the electrical system of the car. There's just the super thick power cable and a much smaller D+ cable (i think).
The alternator connects to the engine block and I'm assuming there is a Ground Strap between the engine block and body. So the alternator ground is via a connection between the Alternator housing and engine block and then engine block to ground strap and then via ground strap to body which is proper ground.

Any idea where I would find this ground strap ?
 
#22 ·
The bad cylinders are going to burn more oil and cause loss of horsepower. You could certainly foul out those spark plugs if too much oil is getting through. I would pull the spark plugs and see if they are fouled and need to be replaced. Use a platinum + 4 spark plugs. At 125,000 km you might also want to think about replacing the ignition wire set as well. I think a simple tune up might solve your problem(s). It doesn't sound like an alternator problem but more like the engine is stalling and causing the alternator light to come on because the engine is no longer turning the alternator properly.
 
#23 ·
Hi visions1,
Thanks for the input. The oil burning part I'm not so sure about. I haven't seen smoke or oil level dropping. But I do suspect that cylinders 1 and 2 might not have had there plugs changed in the last service at the dealership. I trust them as far as I can throw them. i.e. very little trust. Did you know that after 125 000 KM my Fuel Filter was still the original since new, through all those services the Fuel Filter was NEVER changed. I changed it myself recently. So I beginning to think the techie that was servicing my car at the 100 000 KM service was too lazy to get to the plugs right at the back of engine. I'm assuming the cylinders closer to the firewall is 1 and 2 and cylinder 4 is right at the front closer to the radiator.
 
#25 ·
BMW_E46_SA,

I don't think the alternator is the culprit.

Even if the alternator is completely dead, the car can still keep going without missing a beat for around 20 minutes, until the battery is drained. It will not jerk just because the alternator isn't behaving normally.

Somehow your engine keeps stalling/miss-firing. I would check the coils and plugs first if I were you.

I think the cylinders are numbered from front to rear, which means the cylinder closest to the firewall is cylinder #4 in your case.
 
#26 ·
Thanks both scintilla and Poohead900 for your valued input.

I have booked my car in at the stealership for a full diagnostic and work my way from there.

I am also beginning to think the problem could be some where else. I'll start with the CAT sensors, the plugs and coils , then see what happens.

Any idea why cylinder 1 and 2 are behaving badly...do these 2 cylinders share something which is going faulty....at first I though maybe they share a coil pack but later
discovered that each plug has their own coil. So the search continues......
 
#27 ·
Hi All,
BMW issue took a new twist today. While driving back home from the hardware store about 12km away. It jerked twice in quick succession with NO alternator light flashing...I drove another 5km then jerk.then a few meters later..it stalled while I was still driving..which never happened before. I managed to roll to side of the road to safety with hazards flashing.

Anyway..tried starting it...starter turning but not taking...in the mean time the yellow TRIANGLE and the yellow TRANSMISSION gear is glowing. Tried a couple times...it started...yellow triangle OFF but transmission light still ON. Drive home was horrific...each change in gear was a jerk...I then switch to steptronic and drove in 1st and 2nd all the way home. When I get home I switch off...then open the garage door...get back in the car...and all is fine again...no lights..starts fine...it's possessed I tell you..possessed by some demon...probably the AUDI or MERC demon trying to get me to switch over...:)

Spoke to a BMW mechanic...seems to think it could be the AIR MASS FLOW METER because of the TRANSMISSION behaviour ....common on E46 apparently. So I'll get one and hope for the best. Has anyone experienced an intermittent fault on AIR MASS FLOW ?
 
#28 · (Edited)
Hi All,
BMW issue took a new twist today. While driving back home from the hardware store about 12km away. It jerked twice in quick succession with NO alternator light flashing...I drove another 5km then jerk.then a few meters later..it stalled while I was still driving..which never happened before. I managed to roll to side of the road to safety with hazards flashing.
Okay, this is going to sound like the most hare-brained thing you've ever heard, but.....

Check the physical catalyst in your catalytic converter.

I never thought I'd hear anything like this fault again, but when I was younger, some broken-loose honeycombed catalyst (about 1/3 of the total) in my father's truck would occasionally shift and clog the exhaust flow, causing the truck to cough and wheez. It was the weirdest fault anybody had seen, intermittent cutoff (especially around turns) power loss, and even some dying out on the highway. Just about everybody was confused about it, and it wasn't until a sawsall was taken to the exhaust that the truck fixed itself.

I'm pretty sure that this isn't your problem, your car being a BMW and not a 1990 Ford Pickup.

But if the car is befuddling mechanics (both local and stealership alike), you may as well try going ******* on it and cutting the exhaust off.

If it fixes it, the fault that I have never expected to see again has happened!
If not, oh well. The car probably sounds better without exhaust anyways.
 
#29 · (Edited)
BMW_E46_SA and everyone,

I have your same car, an e46 318ci valvetronic (N42B20 engine), I even have 125.000 km as well and it's been 3 months now that I am having your same issue!
At the beginning it was doing it like 2 times in a week, or even less... so I didn't pay much attention this past November when it all started but today for example the situation got worse and the car stopped itself in the middle of the street (for the 1st time), as I red it did for you. I restarted the engine with no problem at all, as if nothing happened, and drove on the way back home.

Lately the car is giving out this problem more often and I don't have a clue on what might cause this, neither my Local BMW dealer could help, earlier this January they made me change the alternator (I then took a refurbished one) and I also changed all the 4 spark plugs and their 4 coils but all this didn't help as you can see.

Well, the issue is always the same: RED BATTERY LIGHT turns on for a couple-three seconds, along with the feeling of a strong engine CUT OFF, as if the car might stop at the time; But then the car keeps going... but until today, it never stopped... Today instead it did... and that scared me.

As solution, did you try to change the MAF yet? Did it solve the problem for you? Or even... have you tried to change the exhaust as suggested by Poohead900? Or I even red in another topic that might be the exhaust CPS...? What does CPS mean by the way?
Hmmm coincidence or not, now that I red such messages, in early October I have replaced my original exhaust with a Supersprint exhaust... and well, in November all these problems started. Very strange... but I don't wanna think it's really the exhaust... but I think its worth a try maybe.

Please help me... I don't know what to do anymore to solve this problem, my big worryness now is that someday the car would not start anymore, if it stops like today! And everytime the red battery light shows for that couple of seconds, and everytime I feel that immediate and solitary CUT POWER, my heart beats... everytime. :tsk:
This can happen at any point, wheter you go slow or fast... but lately I noticed it's doing this more during re-starts from stopping corners or after a brief stop at red traffic lights...

Still waiting for inputs... all togheter we can cooperate.
 
#158 ·
BMW_E46_SA and everyone,

I have your same car, an e46 318ci valvetronic (N42B20 engine), I even have 125.000 km as well and it's been 3 months now that I am having your same issue!
At the beginning it was doing it like 2 times in a week, or even less... so I didn't pay much attention this past November when it all started but today for example the situation got worse and the car stopped itself in the middle of the street (for the 1st time), as I red it did for you. I restarted the engine with no problem at all, as if nothing happened, and drove on the way back home.

Lately the car is giving out this problem more often and I don't have a clue on what might cause this, neither my Local BMW dealer could help, earlier this January they made me change the alternator (I then took a refurbished one) and I also changed all the 4 spark plugs and their 4 coils but all this didn't help as you can see.


Well, the issue is always the same: RED BATTERY LIGHT turns on for a couple-three seconds, along with the feeling of a strong engine CUT OFF, as if the car might stop at the time; But then the car keeps going... but until today, it never stopped... Today instead it did... and that scared me.

As solution, did you try to change the MAF yet? Did it solve the problem for you? Or even... have you tried to change the exhaust as suggested by Poohead900? Or I even red in another topic that might be the exhaust CPS...? What does CPS mean by the way?
Hmmm coincidence or not, now that I red such messages, in early October I have replaced my original exhaust with a Supersprint exhaust... and well, in November all these problems started. Very strange... but I don't wanna think it's really the exhaust... but I think its worth a try maybe.

Please help me... I don't know what to do anymore to solve this problem, my big worryness now is that someday the car would not start anymore, if it stops like today! And everytime the red battery light shows for that couple of seconds, and everytime I feel that immediate and solitary CUT POWER, my heart beats... everytime. :tsk:
This can happen at any point, wheter you go slow or fast... but lately I noticed it's doing this more during re-starts from stopping corners or after a brief stop at red traffic lights...

Still waiting for inputs... all togheter we can cooperate.
I had similar problem; was vacuum leak...torn intake boot after the maf. Car would almost stall when chopping the throttle causing the voltage light to come on intermittently .
 
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