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Pelican Technical Article:

BMW Alternator
Troubleshooting and
Replacement

Difficulty Level: 4
Difficulty scale: Adding air to your tires is level one
Rebuilding a BMW Motor is level ten

 This article is one in a series that have been released in conjunction with Wayne's new book, 101 Performance Projects for Your BMW 3 Series. The book contains 272 pages of full color projects detailing everything from performance mods to timing the camshafts. With more than 650+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any 3 Series owner's collection. The book was released in August 2006, and is available for ordering now. See The Official Book Website for more details.
 
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[click to enlarge]

     One of the nice things about the configuration of the BMW engine is the relative ease with which you can replace the alternator. The alternator is nestled neatly on the left side of the engine compartment and is easily accessible. The replacement and repair process is straightforward and should take you about an afternoon to complete.

     First, make sure your alternator is indeed the cause of the problems with your charging system. Sometimes bizarre electrical problems can be caused by a number of faults other than the alternator. It’s important to troubleshoot the system prior to replacing your alternator.

     The first component to check, then, is the belt that drives the alternator. Is it tight and amply turning the fan? If not, tighten it according to the procedures outlined in Project 5. Modern belts seldom break, but they do get brittle and glazed with age, and can slip on their pulleys. Replace it with a new one if it looks cracked or brittle.

     The next item to check is the voltage at the battery. This should read a little more than 12 volts with the engine off. When the car is running, the voltage should read at in the range of 13 to 14.5 volts with the engine at 2,000 rpm. If your battery appears to be leaking, your voltage regulator has probably failed. The battery will usually only leak acid if it has been overcharged at a much higher voltage. If the voltage measured at the battery is more than 16 or 17 volts when the engine is running, the regulator is probably bad. If your battery has boiled over and has acid flowing out the top, clean it up immediately. Dousing the area with a water-and-baking-soda solution should help considerably to neutralize the acid and prevent it from eating away at the metal.

     An important item to check on your car is the engine ground strap. The engine is electrically isolated from the chassis by rubber motor mounts. If the engine ground strap is missing or disconnected, you might have a whole bunch of problems, including electrical system malfunctions and difficultly turning over the starter. (See Project 85 for the exact location of this ground strap.) Also, some BMW alternators have an external ground that may get disconnected accidentally.

     Almost all the 3 Series cars have a replaceable voltage regulator/brush assembly. If you’ve determined the regulator to be working properly, then you should probably remove the alternator for testing and inspection. Before starting any work, make sure you disconnect the battery. The positive battery terminal is directly connected to the alternator, and it can be dangerous to work on if it’s live (see Project 84).

     The first step in removing the alternator is to remove the belt that drives it. (See Project 5 for detailed instructions on belt removal.) Now removing the alternator from its bracket is a very easy process. On the early 3 Series, the alternator is affixed to the car via a pivot bolt, and a rack-and-pinion assembly is used to adjust the belt tension. Disconnect the rack-and-pinion assembly if your car has one (see Photo 2), and unbolt the alternator from its bottom pivot bolt. For the later E36 cars, the alternator is fixed in place, and the multifunction belt is tightened on the alternator with a spring-loaded tensioner pulley (see Project 5 for details and photos). Simply unbolt the alternator from where it’s attached to the engine after removing the belt. Depending upon which engine you have, you may need to remove some equipment such as the air cleaner and cool air guide located above the alternator. See Project 12 for details on removing components that are in the way.

     With the alternator unbolted, disconnect the electrical connections from the rear. I recommend taking a digital photo of the connections, because many people mix them up when reinstalling the alternator. If you make a mistake and hook them up incorrectly, it’s possible to do some significant damage to your electrical system. Reminder: Do not touch any of these connections while the battery is still hooked up! (Review Project 84 for additional details).

     With the alternator out of the car, remove and inspect the regulator/brush assembly (see Photo 4). If you are replacing the alternator completely, transfer the old pulley assembly to the newly rebuilt alternator (see Photo 3). Installing the new alternator is now simply the reverse of removal. Make sure you reconnect all the wires to their proper terminals when you are done.

     If you would like to see more technical articles like this one, please continue to support Pelican Parts with all your parts needs.  If you like what you see here, then please visit our online BMW catalog and help support the collection and creating of new and informative technical articles like this one.  Your continued support directly affects the expansion and existence of this site and technical articles like this one.  As always, if you have any questions or comments about this helpful article, please drop us a line.

Figure
Figure 1		Here is an alternator nestled into the engine compartment on an E30 318i. It’s relatively easy to reach, although on some models, you may have to remove the air cleaner and some hoses to completely pull it out.
Figure
Figure 2

Shown here is the rack-and-pinion system used to apply tension to the belt on early cars. Loosen the bolt at the rear of this bracket before you try to turn the front toothed bolt. If you don’t, you will break off teeth on the rack and thus make it very difficult to tighten the alternator belt. This particular bracket has been abused and has suffered the loss of one tightening tooth (red arrow).

Figure
Figure 3		I’ve never seen a new or rebuilt alternator supplied with the pulleys attached, so you’ll need to transfer them from your old unit. Removing the pulley can be tricky if you don’t have an impact wrench (good reason to buy an electric one). Also useful may be a strap wrench, which is a handle with a rubber strap on it that can secure and tighten around a pulley. These four frames show the removal and reinstallation of the pulley on an E30 318i alternator. Be sure to take notes as you disassemble the alternator pulley assembly—it must be reassembled in exactly the same manner on the replacement alternator.
Figure
Figure 4		Nearly all 3 Series alternators have a brush/regulator assembly in the rear that can be easily removed and replaced (blue arrow). Remove the brushes and inspect them carefully if your alternator is not working well. If the contacts are short in length, they are worn and need to be replaced. If they are long (as shown in the photo), you probably have some other internal problem with the alternator that’s causing it to malfunction. Replacing this regulator assembly is a good step to take prior to spending money on a rebuilt unit.
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Comments and Suggestions:
SpennykazComments: Hey Wayne, iv got an 1984 318i, my battery light stays on even with the car off, it idles like crap, but it's charging I think I disconnected the power wires from it while running and my idle was perfect, however my headlights are getting dimmer and my stereo won't turn on, the battery light is off with the car off now, however, when running, my park brake, brake fluid and battery light come on. Help? I installed a new rectifier and it's been doing it ever since, the stator had 3 wires connecting it to the rectifier and the new rectifier has 4 hoops to solder the stator to... I soldered them to where it looked like they were supposed to go. I couldn't find any diagrams and I'm at a loss
February 3, 2012
redfiyahComments: My 1995 bmw 318 i keeps losing charge. I have to jump it everyday. The alternator checks as good, this is a brand new batteryactualy the second one because I took the first one back because I thought it was bad/old...how can I find out why the battery dies when sitting for 1 night?
January 30, 2012
kennysugarComments: My 2006 BMW 650ci converterble battery goes flat seems not charging and it doesn't indicate battery or altenator foult on the dashboard, pls wots the problem
January 25, 2012
kennysugarComments: My 650ci convertable battery aint charging anymore yet it doesn't show battery sign on the dashboard, am suspecting my altenator is that the fault?
January 25, 2012
tomasComments: Problem is and has been for some time, that when I turn on the parking lights I don't have to turn on the headlights to cause it, the parking lights suffice to produce it all dashboard lights dim by about three/fourths. they become so dim, especially, for the tach and speedo and gas and temp gauges that they are essentially unreadable. any thoughts? suggestions? could bee the regulator not regulating well? realy with built up resistance? I'm flummoxed. thanks!!
December 29, 2011
 Followup from the Pelican Staff: Hmm, have you tried turning the headlight knob - that typically changes the brightness of the dashboard. When you turn the lights on, they are set to automatically dim on the dash. This is adjustable - the exact method varies depending upon the model of car.- Wayne at Pelican Parts
HornblowerComments: I forgot to tell you that I have a 1989 BMW 325i convertible.
December 21, 2011
HornblowerComments: Your instructions would probably cover 95 percent of the problems. I experienced alternator "failure" due to a bad connection in my instrument cluster. It so happens that when you turn the ignition switch to run or start 12 volts are feed thru the instrument cluster C1 pin 14 connector to power the charge indicator light in parallel with 10 ohm resistor in case bulb burns out and then feed out via C1 Pin 16 to power the alternator field coil. This provides the voltage to create the magnetic field to generate the voltage when the alternator is rotating. A bootstrap circuit provide voltage via steering diodes from the alternator stator to the field coil after the alternator is running then providng a counter voltage to turn off the charge indicator light. In my case, the C1 connector, thru corrosion and old age, created an open circuit that did not allow the 12 volts to go to the field coil. Reinserting new C1 Pins 14 and 16 female pins in the C1 connector fixed the problem. No BMW "experts" could fix this problem. After replacing 3 good alternators and 3 batteries replacements I uncovered and fixed the problem.
December 21, 2011
harryoComments: 96 bmw318is auto when ignition off no horn no brake lights bmw brake switch installed new .
horn and brake lights work when ignition on or car running
December 12, 2011
elioComments: oups i forgot to tell u my BMW is 2006 Model
November 25, 2011
elioComments: hi i just bought a BMW 325i two days ago;
today i tried to open it it wasn't opening.so i opened the door using the small key.
when i tried to enter the key and turn on ignition it was no activating. but all the lights is functioning wich proove that the batterie is still ok.

What do you think the prob is??
November 25, 2011
bimmer1992Comments: Ater replacing the alternator 105 amps original 80 amps on my BMW 316i 1992 model, the siren and tones when arming/disarming or using the panic botton on the laserline 996V3 alarm do not work.
Any ideas? As before replacing the laternator everything worked perfectly
November 10, 2011
firstbimmerComments: hey.. last night in my 1995 325i..car stero speaker stop playin then the abs light started flashing.. then came back then it ran fine ..then it happen again then it completely died. then i let in seat for a while and turn back over .
October 15, 2011
nixta003Comments: Hi there i won a 1993 November release 318i e36 awesome car love it but i am having issue with my instrument cluster the whole thing went out while is was driving even the odometer went out none of the dials work. I have taken the cluster out using instruction from the net and checked for Batteries but there are none i wanted to make sure i checked all the fuses blade fuses and they seem fine, when i disconnected the battery in the boot and reconnected it the odometer came back on actually all the dash lights came back on now they are all still okay and working but the dials are not no speedo no fuel gauge and no temp gauge however i did notice that when i reconnected the battery the fuel warning light has come on and stayed on is there anything you can suggest i also try before i go looking for another one to buy, im enjoying working on my BMW its the first car ive ever worked on, awesome site guys, look fwd to any suggestions you may have
October 14, 2011
JosyComments: I just rebuild my altarnator put it back on and still not charging. Took it back off and had it tested and they say it way good. put it back on and still dosent work. Does anyony have any idea what I sure check nexts?
October 1, 2011
RebeccaComments: Hi there, just bought a bmw 318i 1999 E46 and found that some idiot cut the wiring to the alternator and taped the blue and green wires together to fit a lower amp alternator for an E39 into the car. Can you tell me what the green and blue wires to the alternator are used for? Also, I have replaced the alternator, connected it to the battery, and have also replaced the battery, but still the car dies on me after driving it for about 1 hour, as the new alternator is not charging the new battery. There must be a voltage drop somewhere, but I don't know where to look? Could this be a cabling problem from the alternator to the starter motor? Your help would be greatly appreciated.
October 1, 2011
Adam WadeComments: I have a mystery for you. 1988 325iX, with the M20B25 motor in it.

At idle almost exclusively, the ABS kicks in and out, making the servo sound and raising and lowering my brake pedal. When I am moving and this happens, I have almost no stopping power, even on dry roads. It it intermittent, and when it does happen, it is at an irregular rate, pulses being fast and slow randomly but in quick succession. Sometimes re-applying the brake pedal eliminates the problem, but less than half the time.

Now, the problem largely goes away if the engine is revved above about 1500 rpm.

I checked the voltage at the cigarette lighter. Immediately after shutoff the battery reads about 13.6 volts and it slowly drops to about 12.7 volts over the course of half an hour or so. At idle, the alternator light comes on very very faintly - you can really only see it at night. Voltage at the cigarette lighter at idle is 13.5 volts, and revved above 1500 rpm is more like 13.8 volts.

I added another ground strap from the chassis to the engine block 4 gauge, and the alternator to the engine block reads 0.00 ohms, so I presume it is not a grounding problem. the car does have close to 200k miles on it, with an unknown history regarding the alternator, so it could be the alternator. The battery is about 10 years old, although it was the high-end Interstate battery with the 7 year warranty and very high capacity MTP-91, I believe.

So, I'm thinking it is not the alternator that is the problem here. The battery draining slightly after shutoff worries me a bit, even though it levels off well within the realm of "normal". I'm wondering if replacing the battery is going to be the answer here, or if I should test the alternator, or dig deeper into the ABS system looking for answers here. But I have a sneaking suspicion that replacing the battery may be the right answer. Any ideas, guys?
September 27, 2011
BlunderComments: My 2003 325i does not start and gives only the ABS and seat belt light on dash when key is turned. The engine gives a vibe like something is wrong with the alarm system

I have only one key and has to use it manually to open and start car
September 27, 2011
BlueComments: I have 95 318is bmw that over heated on the highway I added water and it seems that the water was exiting out of a hose in the top center of the engin my brother plug both ends and when I made it home it died on me now ive replace the part the car wont turn on what do I do.
August 27, 2011
eztuner12Comments: Hi!
When do I know is time to change the voltage regulator?
Any symptoms I should look for or notice!
Thx
August 19, 2011
tomComments: I have 530XI 2006, I don't understand why my generator fan kicks in when I started the engine and it would run for several minutes, and there is not indicator light on my dash board. Please advice, and thanks in advance.
August 10, 2011
AlexComments: I have an '87 325es and it was marking 18-20 volts with the engine off it cranks but wont start, so i changed the alternator and the system still reads 18-20 volts, engine off. Last I checked and no power is getting to the dme when key is on Run, but it gets power at Acc. Could this be a short?
August 7, 2011
eztuner12Comments: Hi Wayne
First I have to congratulate you for the fine team force you have at the shop. I have placed a couple of order thru your e-shop and it has been a superb experience ļ
My issue this time is, that any time my radiator primary electric fan turns one all the lights on the car dims. This happened when the car is in idle @800RPM even the A/C cools less at this point. Once I reeve the car up to @ 1000RPM or more everything goes back to normal. Battery seems to be on the right voltage and it keeps charged always. I removed the Alternator an OEM Valeo 80 Amp and I checked the brushes for wear but they seemed to be ok. The alternator is 15 years old but the car has only @ 23,400 run miles since I got the car new. Do you think that the alternator regulator may be causing this lights dim scenario even if the brushes look well?
Perhaps any other part I should check, go for a new regulator or new alternator perchance? Can I go with the Valeo 105 Amp you have on your catalog?
My car is 1997 e36 M44 318is VIN # AS71156. Just in case you need the info to recommend me a part or what I should do.
Thank you
August 3, 2011
mikeComments: For the past two months I've been changing my fuel tank and steering rack. After I completed the job with the batt disconnected I started her up and apart from the rough idle she ran ok got a bit better when hot... Then the lights went out and the car died and wouldn't crank. I jumped it and she runs fine, put a charged batt in and runs fine, until it loses charge and dies. My car ran just fine before I changed the fuel tank and steering rack. How did the altinator die?????!!And I've checked the engine ground wire
July 10, 2011
joshdudeComments: Hi I have a 2003 325 ci, new alternator and battery. Now here is a little preview of how I found out I was having a problem. I had my radio on the other day and it kept cutting out every time I used the turn signal. Upon further investigation I only had 12.2 to 12.8 volts running at the battery and the same at the alternator. Now when I lift the hot lead off the battery when car is running the voltage jumps up to 13.2 to 13.6 volts. Tried this with two different batteries with same result 12.2 to 12.4 with battery connected and running and 13.2 to 13.5 with car running and battery not connected.
Thanks for reading josh
July 8, 2011
sideeffektComments: Sorry, car was an 87 325es, with original Bosch alternator. The original alternator grounded and was metal on metal at all mount points.
June 15, 2011
sideeffektComments: 'Auto parts store Checker/O'Reilly is selling alternators with electrically isolated mounting holes - there is a rubber grommet separating the mounting holes from the rest of the alternator, preventing the bolts from grounding the alternator like they should.'

I ran into this same problem with an Ultima remanufactured alternator from Checker. Solution was running an 18gauge wire as a ground from a bolt that sticks out a little further on the back of the alternator, up to back side of the tensioner bracket between that and the alternator mount. Battery was too dead to start before I ran the ground, afterwards, it started right up.
June 15, 2011
shawnComments: I have a 94 318i, i have a problem with pulsating lights which i believe could be the voltage regulator, am i correct? Secondly my biggest problem is that when i start my engine cold, the car runs fine, but as soon as i warms up it starts to sputter....once the rpms get around 2000 it runs great.....could this also be linked to the pulsating lights or the voltage regulator....or just the ignition coil?
June 6, 2011
TiffanyComments: I have a 1999 323i bmw. My alternator went out and i let it sit for about 2 weeks before replacing it. I started it occasionally and it started fine. I let it sit for a whole week without starting it at all and it started but would not stay idold. I replaced the alternator and it still wont stay idold. What is it and what do i need to do to fix it.. Please help
June 5, 2011
Easyas123Comments: How cam I regrease or replace the front bearing on alternator for a 1993 325i?
Noise is not noticeable, but sounds dry and feels worn when spin by hand.
I extended the life by replacing the regulator/brushes.
June 4, 2011
MelissaComments: I have a 1999 BMW 328i and I recently changed out the alternator as I was originally told the alternator was bad. Now I was haveing the same problem with having to get a jump everytime I shut off the car, I went back and had it the alternator tested again and it said my regulator was bad. Where is the regulator and how do I replace it?
May 25, 2011
VictorComments: I have a 2006 M3 convertible, at high rev the battery light comes ON, during idle its fine, I also noticed when I rev high when engine is cold no battery light, so I see it only when high reving and engine hot, may this be alternator problem?
May 6, 2011
RodmanComments: Ok I have a 1990 with an 87 325i engine in it. The belt snapped off and I didn't notice until the next day when my cars lights and raideo started to dim and cut off. I replaced the belt and it still wouldn't hold a charge. Replaced the battery drove fine for a day then did the same thing with lights and radio. Replaced the alternator twice and it still won't hold a charge. I've checked the entire charging system and I have connection every where. I have been working on it for three weeks and I'm stumped also checked all grounds any help would help thanks
April 12, 2011
 Followup from the Pelican Staff: I would check the charging voltage at the battery to start. This will tell you if the alternator is attempting to charge the battery. I would also triple-check all the grounds using an ohm-meter. Measure the resistance between the battery negative terminal and the housing of the alternator - should be zero. - Wayne at Pelican Parts
CharlesComments: I have a BMW 318i...the wiring was cut to the alternator....The ? is which wires go where?
April 6, 2011
 Followup from the Pelican Staff: Sorry, I don't have a wiring diagram handy (you didn't mention what year your car was). - Wayne at Pelican Parts
tayComments: Okay, for three days i've been trying to replace my 1995 530i alternator, and have failed to even remove the old one. I'm getting deeper and deeper into the disassemlbly of surrounding components, and am frustrated with the difficulty of what should be an easy job. This is the first time I've ever seen an alternator mounted on the bottom with it's own air intake. Can post pics if helpful. Any advice would be appreciated, thx!
March 9, 2011
 Followup from the Pelican Staff: I'm going to copy this question to our forums and send you a link. If you can go there and post some photos, perhaps we can help you decipher this. - Wayne at Pelican Parts
Al3xe36Comments: Could i replace the alternator on my 1995 318i its 80 amps to a 140 amp one. Also the reason I'm replacing it is because someone told me the bearing is going bad so it whistles is that true?
March 8, 2011
 Followup from the Pelican Staff: In theory, the alternator should only supply as much current as is drawn by the system. In other words, if you have an 80 amp unit and your draw is only 40 amps, then you can use anything above 40 amps and it will be fine. People typically install a higher amp alternator when they are installing a big stereo system, or higher power headlamps. So yes, installing a higher output unit should be fine.

On some more modern cars they will sometimes trigger an alternator lamp when you install a higher amp unit as they are not expecting the alternator to be charging above it's expected level. - Wayne at Pelican Parts
denComments: I replaced the voltage regulator on my '03 325xi, now the car will not start,the starter is cranking but it wont fire? There was no problem before replacing the VR and I'm wondering if there are fuses related to the ignition system that should be checked where they are located? Everything else was reconnected. Thanks
March 6, 2011
 Followup from the Pelican Staff: I'm going to post this question over to the forums, and perhaps you can add some more details there. Why were you replacing the regulator, what was wrong with the old one? Did you disconnect the battery prior to working on the car? Did you check all the fuses to make sure that they were still functional and not blown? - Wayne at Pelican Parts
frustratedComments: I have a 1995 318i. I have a battery drainage problem. Its a brand new battery and the alternator was tested 4 different times at 4 different places. It tested out fine. The battery light is on, then the alternator modular light turns on then the car dies. Left overnight, it starts works fine but can die anytime. what could be wrong?
March 2, 2011
 Followup from the Pelican Staff: It could be just about anything, but I would start by checking the ground connections. Measure the resistance from the engine to the chassis - it should be very low. Verify that your ground strap is in place and fastened properly (maybe remove it and clean it up with a wire brush?) - Wayne at Pelican Parts
joshComments: hi was wondering were i can get brushes for my 2003 325ci
alternator. thanks
March 2, 2011
 Followup from the Pelican Staff: Unfortunately, the newer-style alternators are not user-repairable (they don't sell the parts separately). You have to buy a whole new unit. - Wayne at Pelican Parts
Scott1981Comments: I have an 04 325ci and red battery light keeps coming on from time to time. The car still runs and after I drive it for 5 mins or so, I turn off the car and turn it back on and the light stays off for a few days until it decides to come back on. I don't notice a loss in power either. What could this be?
February 27, 2011
 Followup from the Pelican Staff: I'm not sure - it could be the battery, or it could be the alternator. I would probably replace the battery first and see if that fixes the problem. If the battery is original, it may be time to replace it anyways. - Wayne at Pelican Parts
Vladae46Comments: Hi,
The challenge I am having with my alternator is noise, lots of whining noise. It charges fine, no issues. Sounds like a bearing that is shot. Can I replace the bearing only?
2001 E46 325Ci.
Thanks.
February 13, 2011
 Followup from the Pelican Staff: Sorry, no, the bearings are not available separately. The best recommendation I have is to remove the alternator and have it checked at a repair shop that can possibly regrease the bearings or at the very minimum confirm that it is indeed the alternator that is making that noise. It can be difficult to tell with 100% certainty that the alternator bearings are making the noise (and not perhaps another component in the engine). - Wayne at Pelican Parts
JohnComments: '90 BMW 325is died while driving. First lost wipers, dash lights/gages, radio, heater blower then finally engine cut out. Suspect bad alternator. After getting it home I hooked up jumper cables to another car and jumped it note: battery is very low on charge. Ran fine until I removed the neg cable - died within a few seconds. I'm thinking that the alternator died and I was running off battery until charge ran too low. Does it make sense to check anything else like voltage regulator or does this sound like a bad alternator? Looks like I could take the voltage regulator/brush assy out without removing anything else and check it first to save possible unneccessary work. Is there an easy way to check it? Also, if I buy a new/reman alternator will the voltage reg come with it I think it would, right?. Thanks.
February 7, 2011
 Followup from the Pelican Staff: With issues like these, I like to start with the cheapest and easiest thing to fix - the battery. I would recommend testing and/or replacing the battery to make sure that it can hold a proper charge. Also check the voltage coming out of the alternator - if the voltage is too high (let's say 15-16 volts or higher), then it may be overcharging and damaging the battery (which causes it to fail more rapidly). On the new alternators, the voltage regulator is indeed built-in to the unit. - Wayne at Pelican Parts
RichardComments: Hi.
I'm looking for all grounds wires on my 1997 e36 318is. I look up "project 85" as suggested on the article but nothing comes up on project 85 page regarding ground wires locations.
Can you please tell me where can I find all ground wires on my car model?
Advanced thx....
February 2, 2011
 Followup from the Pelican Staff: There are something like 30 or so ground points in the car. I'm not sure exactly what you're looking for, or trying to accomplish? - Wayne at Pelican Parts
SakariiComments: I have a 3 Series 2000 BMW with 150k miles. When I got out of work I got stuck in snow for about 30 minutes and when I arrived home I got stuck once again for another 30 minutes. While switching gears from reverse to drive on my drive way I noticed the alternator/battery light turn on and now I cant turn my tires in any direction. Any ideas what it could be? Battery? Alternator?
February 1, 2011
 Followup from the Pelican Staff: Hmm, are you sure it's the battery lamp, and not the transmission lamp? The transmission lamp is a little gear that lights up. Seems that would be more likely. Showing a battery lamp after what you described here, I don't have any clue as to what would have caused that... - Wayne at Pelican Parts
denComments: I'm ready to replace the VR Valeo on my '03 325xi wagon auto.
Please confirm if this can be done without removing the alternator?
January 22, 2011
 Followup from the Pelican Staff: I'm pretty sure that you need to remove the alternator to reach the voltage regulator. On your car, I'm pretty sure that the voltage regulator is located on the back of the alternator. - Wayne at Pelican Parts
rubzComments: hi there, i have a 318i m-sport. Whilst im driving the battary light comes on and soon after that my hand break and ABS Light comes on. Most of the time the lights go after i rev the car but now the car jst cuts itself off i then have two jamp start in order for it work.
January 20, 2011
 Followup from the Pelican Staff: This certainly sounds like an alternator problem. Or, it could be a battery problem. I would check the battery first, and make sure that it's operating properly, then move on to replacing the alternator. Also check to make sure there is a good ground connection between the alternator and the battery. - Wayne at Pelican Parts  
EricComments: How do you disconnect the wiring from the back of the alternator? I've tried pulling and prying, but am afraid I will break something. 91 318i
January 12, 2011
 Followup from the Pelican Staff: You just need to get in there and maneuver it out. On that car you should be able to reach in from behind with the proper tools (might need some angled wrenches). - Wayne at Pelican Parts
GremibleComments: On a 1983 533i a new battery started dying overnight. Connecting an ammeter between the battery and chassis with the key off I found something was drawing 3.5 Amps! It took awhile to isolate it to the alternator. With the car running, the voltage was 13.5V so I thought the alternator was O.K. I took it out not so easy on this car and O'Reilly's tested it as good, but near the bottom of the spec. I replaced it with a rebuilt unit and the current drain was down to 200mA another issue. I suspect one of the six diodes 3Øwas shorting giving a leak path to ground but still allowing enough current to charge some from the other two phases.
November 26, 2010
MattComments: I wanted to follow-up one more time in case anyone else ran into problems like this. Running a large ground wire off of one of the mounting bolts did not work!! It turns out that the auto parts store Checker/O'Reilly is selling alternators with electrically isolated mounting holes - there is a rubber grommet separating the mounting holes from the rest of the alternator, preventing the bolts from grounding the alternator like they should. With the help of a friendly employee, I found my old alternator the core was still there and sure enough the bolt holes were continuous with the rest of the alternator case. With luck on my side, I removed the brush/regulator from the back of both alternators, and put the brush/regulator from the "new" alternator onto the "old" alternator. With the new brush/regulator the old alternator PASSED when it was tested!! The brush/regulator was the only bad component, so my recommendation is try buying one of those separately and install it if your alternator is bad - it very well may be the problem. The store refunded my money for all the hassle over 2 days of work and I left with a repaired old alternator. Installed in and finally it works, this is solve once and for all!!!
November 21, 2010
 Followup from the Pelican Staff: Most alternators are indeed wired with a separate ground connection, so this seems odd to me, although I'm not sure which car you're working on. Bottomline, check the resistance between the alternator and the battery ground prior to replacing the alternator or voltage regulator. - Wayne at Pelican Parts
MattComments: For the reference of anyone who reads this, and may ever be troubleshooting an alternator, I solved my problem. Even though I cleaned the mounting bracket with a wire brush and everything looked shiny and conductive, the alternator was still not grounding properly. I ran a wire 4 awg battery cable from the alternator to the chassis to ground it, and IT WORKS. Nice to solve these long drawn out problems!!!

One more note: I looked into it and the capacitor is NOT critical to the function of the alternator. I believe it is just to reduce noise. Hope this information is helpful.
November 20, 2010
 Followup from the Pelican Staff: Thanks for the feedback Matt. I tell *everyone* troubleshooting an alternator problem that they should check the resistance from the alternator to the battery ground first, and make sure there is low resistance there. - Wayne at Pelican Parts
Matt Comments: My girlfriend left the lights on all day on my 1987 BMW 325i. It was dead, and when trying to jump start the car, the engine would die whenever the cables were removed. The batter then didn't seem to be holding charge so I got a new one and installed it. The car started and ran but the alternator was not charging the battery Voltage decreased from 12.6 to 12.0 volts instead of increasing to 13.5 with car on.

I took the alternator off and had it tested. The store employee told me it was bad and then sold me a new alternator. I put the new alternator on and was still having the same problem, not charging the battery. On the off-chance that the new one was bad, I took it off again and had it tested. It passed. I cleaned the bolts and mounting brackets and reinstalled the alternator hoping to solve a bad ground problem. No luck. My engine ground strap looks fine and has negligible resistance. I had a glance at a wiring diagram for the car and of the two wires going to the alternator the larger wire runs to the starter and is hot at all times shows same voltage as battery car on or off. The smaller wire runs to the ignition switch and has no power unless the ignition switch is turned on, at which time it shows about 0.5v less than the battery.

The pulley and belt are fine and spin at the proper speed when the car is on. I checked the resistance on the wire between the starter and alternator and there was negligible resistance. I even pulled a working battery from another vehicle to see if somehow my new battery was bad new battery is fine, just no charge being supplied from the alternator. I can't think of what else to check and am really frustrated. The fuses are fine... wiring looks fine to me. If I start it the engine will die if the negative battery cable is disconnected, which I thought indicated a bad alternator, though the alternator passed the testing.

There is a small black case with a short wire and plug on the back of the alternator which I transferred from the old alternator to the new. I believe it is a capacitor, but I'm uncertain if or how it affects the alternator performance. Could it be bad, and be causing the alternator not to work? What other possibilities are there? Could the new alternator be bad even though it tested good once??? I am so frustrated, any advice would be truly appreciated. -Matt
November 20, 2010
JimmyComments: I have a 2004 BMW 325I, alternator idle is 13.8 before driving everyday, then idle voltage dropped gradually after driving. If I drive a little long, idle voltage drops below 13.0 no charging and drain the battery. I already replaced factory belt, pulley, battery and alternator is ok, however, this problem still not solved. Even strange thing is the battery warning signal never on. Can anybody help me
November 14, 2010
 Followup from the Pelican Staff: If the voltage is 13V, it should be still charging a 12V battery. If you are simply measuring voltage using the dashboard gauges, then you might have an issue with your gauge - these are typically not very accurate. Also, when the car heats up, the resistance in the wiring changes (becomes more resistive). If you have corrosion on some components (like a ground strap perhaps), then the addition of heat may change the grounding effects. This is just a guess of course, but it sounds like your problem may be heat-related. - Wayne at Pelican Parts
willowComments: I DRIVE A BMW 2002 318i the battery light came on then there was loss off power, had my car towed to bmw dealership,they replaced the alternator, the next day went to drive it battery light came on again and lost power for a moment, took it back they did a diognostic test couldnt find anything, drove home. Next day did same thing. Should things be going on like this just after having a major service done on vechicle,and why would my car still be playing up.
November 6, 2010
 Followup from the Pelican Staff: Although shops like to opt for more expensive work, I typically replace the battery first when I'm having problems like these. Modern batteries tend to act a lot more quirky than the ones in the old days. - Wayne at Pelican Parts
JimmyComments: Can I replace a 150 amp alternator with 120 amp alternator. I really can not find a 150 amp one locally.
October 26, 2010
 Followup from the Pelican Staff: Yes you can, although the battery may wear down if you have a big stereo or a lot of other electrical drains on the system. - Wayne at Pelican Parts
L.T.Comments: I unknowingly replaced my alternator after hearing a loud whistling noise in that area. It ended up being the idler pulley that needed replacing. anyways everything was fine for months then all of a sudden my battery light kept turning on and off sporadically. There's no loss of power or dimming of lights, but every once in a while my car will not start. The battery is less than 6 months old. I've also recently replaced the drive belt. Am I supposed to tighten the belt more than the tensioner does? any ideas???

Sorry. Never included that it was a 2000 323i sedan
October 22, 2010
 Followup from the Pelican Staff: The belt is self-tensioning. It may be a problem with the tensioner that you replaced, or the belt too. Also, make sure that the grounding between the alternator and the battery is good - check it with a multimeter. When installing the new alternator, the ground connection may have become corrupted. - Wayne at Pelican Parts
harisComments: i have BMW 318i 2002 with 120A valeo alternator, and its having problems so i have to change but when i bought new its coming with 2 pins, but mine is having single pin connector. so what is the best solution?? is there any plug converter is available for this item? or i have to look for the same alternator?? but the problem this alternator is very hard to find i think even there is no any part number sticker on the old alternator. so please write a suggestion.
thanks
October 18, 2010
RobertComments: Looks sounds like my Wife's 2005 325Ci needs an alternator pulley not idler. Bought one from the local dealer and should get some time later this week. I've relaced the idler and tensioner pullys a couple of years ago. Without being able to see adeqately at this point, even with the airbox out, can you tell me thype and size of drive for the retaining bolt? And, are there any tricks to loosening the bolt?

Thank you in advance,

Robert
October 11, 2010
harisComments: thanks for your quick reply. but have you ever seen such a problem??? because of this recently i changed the battery, but it was not helping. did u check the video? but when i start the second time there is not any kind of problems. but are u sure is it with voltage regulator or alternator?
October 6, 2010
 Followup from the Pelican Staff: Could also be a grounding problem. Weird electrical problems are tough to track down and diagnose, as you have discovered! - Wayne at Pelican Parts
harisComments: My bmw 318i 2002 2.0 is showing high voltage above 17v in cold starting, even my dash lights are flashing in my first start, but if i start again after 2 min the voltage will be showin 14v to 14.3v. so what will be problem of this???
Please see the video..thanks
http://www.youtube.com/watch?v=-UjSAXbGvGo
October 5, 2010
 Followup from the Pelican Staff: That seems quite odd, I would guess it has something to do with the voltage regulator going bad? - Wayne at Pelican Parts
DanieleComments: Hi,
I have a 323ci that never had problem, but last night it turned on, i moved it for 5 feet and then it lost RPM and turned off. Now it does not turn on. The battery is ok, the oil level is ok... I am kinda scared: bmw parts are so expensive!!!!
September 23, 2010
 Followup from the Pelican Staff: See what codes the car is putting out, it will probably show you a few: http://www.pelicanparts.com/bmw/techarticles/Mult-Code_Reading/Mult-Code_Reading.htm - Wayne at Pelican Parts
RobComments: Hi, I own the 101 projects book and it has been of great help! However, I finally have a problem that I can't figure out what's causing it. My 1989 325i died while running last night after driving on some high elevation gravel roads. The car showed the usual signs of a failed alternator... lights dimmed, and then the car finally died got it started with a jump, died 5 minutes later. The battery light never came on it does in accessory mode so the bulb is not burned out and I had both the alternator and battery tested and they turned out fine although of course the battery was drained. Any ideas what's causing me to lose power?

thanks,
Rob
September 18, 2010
 Followup from the Pelican Staff: Hmm, it *does* sound like a classic alternator problem. When you had the alternator tested, did they check the voltage regulator too? That's important as well. Other than that, perhaps your ground strap is loose. The ground connection between the engine and chassis should be minimal, otherwise the battery won't charge. Check the strap and then maybe the wire harness after that (clean the battery terminals too). - Wayne at Pelican Parts
Mike82Comments: 97' 328i Hydrolic belt tensioner.
There is a "Cricket" noise coming from under the hood, I replaced all belt bearings and the noise is still there. The noise seems to be coming from the alternator area. If I turn on the headlights or A/C, the noise gets louder. Could this be a an alternator problem?
September 18, 2010
 Followup from the Pelican Staff: Yes, it might be an alternator issue. I would take the alternator out and have it tested - they can check both the output and the bearings inside the alternator. - Wayne at Pelican Parts
overmyheadComments: i have a 92 318i runs fine alternator tested good but wont charge battery...got new battery n same deal when running shows around 12.5v but as soon as u turn car off it wont restart n battery shows 6v
September 7, 2010
 Followup from the Pelican Staff: Check to make sure your ground strap is properly connected. This is probably the source of your problems. Without the strap, the alternator can't complete the circuit and will only slightly charge the battery. - Wayne at Pelican Parts
calvinComments: i have a 1993 bmw 318i and was running fine when i drove to the store and then when i arrived i couldnt roll down the window unless the door was open and then after i turned the car off it wouldnt turn over at all i tried a new battery and still nothing different all the accessories work now windows stereo any ideas what is wrong
September 5, 2010
 Followup from the Pelican Staff: Sounds like some odd electrical problems. I would start checking for wire harness problems, like the one in Figure 2 of this article: http://www.pelicanparts.com/bmw/techarticles/101-Projects-82-Electrical-Problems/101-Projects-82-Electrical-Problems.htm - Wayne at Pelican Parts
B3M2W8iComments: I just replaced the serpentine belt and the battery in my 97 E36 and now the car won't start. Any guidance?
August 18, 2010
 Followup from the Pelican Staff: If the car is not turning over at all, then I would check the connections to the battery to make sure they are tight. Also, check to make sure the battery itself is good and charged. If the car is turning over, then you probably need to check the error codes generated by the DME. - Wayne at Pelican Parts
daxus99Comments: Hello my 95 BMW 318IC started giving me power problems yesterday. Radio was shutting on and off and I started loosing power in acceleration along with a check engine warning light and other errors in which case my car completely turned off. It started up with a jump start and then died again after 5 minutes. Alternator problem?
August 5, 2010
 Followup from the Pelican Staff: It could be either the battery or the alternator. I would probably start with the easier one of the two (the battery) - remove it and have it checked out at a shop, or if it's old, then simply replace it. Then, if the car still keeps having problems, then I would look at testing or replacing the alternator. - Wayne at Pelican Parts 
the alvnComments: I've recently had my 1995 325is shut off on me while driving. I recharged my battery to 12.46 volts, tested my charging system and it stayed at 12 volts. Now, I know the reason for this is due to the faulty alternator. My problem is that this vehicle could be equipped with an 80 amp or 140 amp alternator. What's the benefits of the 140 over 80 amps? How do I know which one is the stock item?
August 3, 2010
 Followup from the Pelican Staff: The 140 unit can be used to power more "stuff" like a big stereo unit. Most likely you have an 80-amp unit in your car, although if you install a higher amp unit, it should only draw what amperage the car needs. Although I have heard of people trying to install the higher amp unit and having electrical gremlins after that. - Wayne at Pelican Parts
tedrienComments: Where can I find out, or can you show in pictures/tell me how to replace the alternator belt on my 1993 318i?
July 20, 2010
 Followup from the Pelican Staff: Here you go: http://www.pelicanparts.com/bmw/techarticles/E36-Belt-Replacement/E36-Belt-Replacement.htm - Wayne at Pelican Parts
DeeComments: While driving car started to cut out then jump forward and eventually cut out altogether. Still turning over for few mins before completely dying. jumped the battery and car started ok but dying again day after. I will fully charge battery for now but think more permanent problem. Any ideas welcome please ? 318Ci 2.0l 2001
June 24, 2010
 Followup from the Pelican Staff: Yes, that sounds like it might be an alternator problem. Test the charging voltage to see what the alternator is putting out, should be 13-15 volts when charging. - Wayne at Pelican Parts
1994318isComments: My 1994 318is produced in 11/1993 reads a voltage of 15.5 to 16. So I understand from previous responses that the voltage regulator is bad. My two questions are:
1. Knowing that this is the original 16 years old alternator, am I better off replacing the whole alternator since it is doomed to fail eventually or should I just replace the voltage regulator?
2. Can I still drive the car mostly highway high rev while the order is being shipped or will this cause serious damage i.e. fry the DME/ECU etc..? Thanks.
June 20, 2010
 Followup from the Pelican Staff: That reading is a little high, but not super high. It does sounds like the voltage regulator is going out though. I doubt it will damage your DME or other components, but it might cause overcharging of your battery, which can then lead to acid spilling out. I would swap out the regulator. - Wayne at Pelican Parts
WerkshopComments: My lights have this pulsating thing going on. I put in a fresh Bosch Alt in not to long ago. Belts were changed too. I checked looseness in my relays, and cannot seem to find out what is going on. Car starts fine, but the intermittent pulsating of cluster, and low beams are annoying.
April 28, 2010
 Followup from the Pelican Staff: I would check the grounds. Check the ground from the alternator to the chassis. Measure the resistance from the negative battery terminal to the alternator housing - there should be very low resistance there. Also check the grounds on the back of your gauges. Take the housing of the gauge and test it to the battery negative - it should be low - the same as the alternator. If not, then that is probably your problem. - Wayne at Pelican Parts
diy4lifeComments: Wayne I bought your book and its awesome, anyone who owns an e30 or e36 should have one. Now for my problem. I purchased a new battery 9 months ago, its now dead. I checked the voltage when the car is running, its only 11.5 or so volts its around 9.5 volts when the car is off. How do I determine if its the voltage regulator or the alternator itself.
April 25, 2010
 Followup from the Pelican Staff: The E36 alternator has the voltage regulator built in. If the regulator is bad, then the voltage is usually high. If the voltage is low, then it might be the alternator itself. - Wayne at Pelican Parts
ccazenavComments: Hi, In my BMW M5 e34 It´s necessary to take the alternator out of the car if I want to replace only the voltage regulator? Thanks.
March 25, 2010
kenComments: I drive a BMW 318I - 2003 MODEL - lately while driving the engine cuts off and a red light appears for a few seconds then it goes again - couple of time it also stalled and I had to stop for a few minutes but it get going again after switiching the car off about 5-7minutes.It has any original battery. I did tighten the terminals but it still playing up.
What should I do next.
January 28, 2010
alComments: Battery not recharging, replaced battery and voltage regulator, but the charge is still intermittent
January 16, 2010
AlComments: battery on 2004 BMW M3 starts recharging only after 10 minutes ride.
Replaced the battery and the voltage regulator - the problem still exist.
What else can I check? Thank you
January 16, 2010
31isamComments: can u replace a 80 amp alternator with a 105 amp unit or will this be too much for the electrical system? i have a 1995 318i m42 and i am replacing the bad 80 amp unit as we speak.
December 16, 2009
 Followup from the Pelican Staff: It's quite common to replace lower amp alternators with higher ones when you're installing aftermarket stereo equipment, etc. However, unless you have any new electrical loads on the system, I would stick with the stock alternator. In theory, the car's bus should only draw as much power as it needs, but with these modern cars anytime you change something like this, there are often side effects. - Wayne at Pelican Parts
AndrewComments: i'm trying to replace the mount bushings, but there is a metal tube with lips at both ends, won't come out....how do i replace the bushings?
October 17, 2009
 Followup from the Pelican Staff: Hi there. As far as I know, these are not replaceable. They are also a non-moving part so it's unlikely they would wear out, unless the alternator was not tensioned properly through it's life. - Wayne at Pelican Parts
325i/1993Comments: Where can I find the engine ground strap for my 1993 325i?
October 8, 2009
 Followup from the Pelican Staff: It's attached to the right side engine mount on your car. I have a photo of this on page 229 of my 101 Projects Book. - Wayne at Pelican Parts
BridgetteComments: What about the 7 Series - is it the same procedure?
September 18, 2009
 Followup from the Pelican Staff: Yes, it should be very similar to the one detailed here. - Wayne at Pelican Parts
StixxComments: Can bearings be replaced also ?
May 20, 2009
 Followup from the Pelican Staff: Yes they can be replaced, but an alternator shop usually needs to do this as there are no "bearing repair kits" that I am aware of. - Wayne at Pelican Parts
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