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BMW Alternator Replacement
 
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Pelican Technical Article:

BMW Alternator Replacement

Nick Czerula

Time:

3 hours3 hrs

Tab:

$300

Tools:

Set of sockets, 13, 16mm E12, T60 Torx, flathead and Phillips screwdrivers,

Applicable Models:

BMW 325i Sedan (2006)
BMW 325xi Sedan/Wagon (2006)
BMW 328i Coupe/Conv (2007-13)
BMW 328i xDrive Coupe (2009-13)
BMW 328i xDrive Sedan (2009-11)
BMW 328i xDrive Wagon (2009-12)
BMW 328i/xi Sedan (2007-11)
BMW 328i/xi Wagon (2007-12)
BMW 328xi Coupe (2007-13)
BMW 330i/xi Sedan (2006)
BMW 335d/i/xi Sedan (2007-11)
BMW 335i xDrive Coupe (2009-13)
BMW 335i xDrive Sedan (2009-11)
BMW 335i/is Coupe/Conv (2007-13)
BMW 335xi Coupe (2007-13)

Parts Required:

Alternator, drive belt, idler pulley

Hot Tip:

Work with a cool engine.

Performance Gain:

Car will charge properly

Complementary Modification:

Change serpentine belt, idler pulley.

A faulty or failing alternator can cause many problems; from a simple discharging of the battery to an engine drivability problem. There are a few signs and tests you can perform to determine if the alternator is the main cause of your problem. If you get lucky, your battery light (charging system indicator) will illuminate to warn you of a possible failure. When the battery light (charging system indicator) is ON, this means a voltage difference has been detected between battery positive (+)constant (terminal 30) and ignition ON circuit (terminal 15), indicating a fault in the charging system.

It is common for an alternator to fail slowly, when this happens, your symptoms will be present when the electrical system has the highest load, for example at night when headlights are on. Driving at night, you may notice the instrument panel lights dim, or the radio or headlights flicker. This is a good indication that the alternator cannot handle the excess load. Another sign of a charging system problem is headlights or radio dim when lowering your window. When the alternator can no longer charge the battery, you may park your vehicle and not be able to start it. Of course this could be a faulty battery too.

Always check the voltage of your charging system under load, voltage should be within 13.2: 14.5 volts d/c. To load, have engine running at idle, turn on headlights and HVAC blower motor. Never disconnect a battery cable while engine is running to test alternator, you may cause damage to alternator or other electrical components from the surge in amperage. Before performing any tests to your alternator, charge and test your battery. If the battery is faulty, your alternator tests will not be accurate.

In this article, I'll go over the steps involved with replacing the alternator on the BMW N52 and N54 engine. I am going to describe how to remove on the N54 engine, there a few differences between the normally-aspirated and turbo-charged engines. Be sure to work with a cool engine and disconnect the battery before beginning. E90 models can come with a few alternator amperage ratings. Be sure your replacement alternator has the same rating as faulty unit. You can usually find the amperage rating on the alternator housing.

Working in trunk, disconnect battery negative cable and cover battery terminal so cable does not accidentally come in contact with disconnected cable. See our tech article on battery replacing for notes on disconnecting and reconnecting battery.

Remove drive belt. See our tech article on drive belt replacing. Mark direction of belt rotation before removing if reusing belt. When replacing alternator, you only have to remove alternator drive belt from alternator pulley and move aside, it does not have to be removed from the engine.

Remove electric cooling fan. See our tech article on electric cooling fan replacing.

Next you will have to remove the air filter housing. Use the steps below that apply to your E90 model. Then pick up where the steps apply to all E90 models.

Models without turbo-charger
Working at front of radiator support, remove two T20 Torx fasteners for the intake duct.
Figure 1

Working at front of radiator support, remove two T20 Torx fasteners for the intake duct. (green arrows)

Working at intake air duct connection at air filter housing, using a small flathead screwdriver, release retaining tabs on each side and pull duct off.
Figure 2

Working at intake air duct connection at air filter housing, using a small flathead screwdriver, release retaining tabs on each side and pull duct off.

Then, pull intake duct out of radiator support and remove from vehicle.
Figure 3

Then, pull intake duct out of radiator support and remove from vehicle. (green arrow)

Then loosen hose clamp (green arrow) and remove two 10mm air filter housing fasteners.
Figure 4

Then loosen hose clamp (green arrow) and remove two 10mm air filter housing fasteners. (yellow arrows)

Disconnect mass air flow sensor electrical connector by releasing tab with small flathead screwdriver and pulling connector out of sensor.
Figure 5

Disconnect mass air flow sensor electrical connector by releasing tab with small flathead screwdriver and pulling connector out of sensor. (green arrow)

Remove air filter housing from vehicle by lifting up and disconnecting duct from mass air flow sensor.
Figure 6

Remove air filter housing from vehicle by lifting up and disconnecting duct from mass air flow sensor.

Models with turbo-charger
Working at front of radiator support, remove two T20 Torx fasteners for the intake duct.
Figure 7

Working at front of radiator support, remove two T20 Torx fasteners for the intake duct. (green arrows)

Working at intake air duct connection at air filter housing, using a small flathead screwdriver, release retaining tabs (green arrow) on each side and pull duct off.
Figure 8

Working at intake air duct connection at air filter housing, using a small flathead screwdriver, release retaining tabs (green arrow) on each side and pull duct off. Then, pull intake duct out of radiator support and remove from vehicle. Picture 9: Working at front of air filter housing, squeeze connector and pull to disconnect vacuum hose, then pull vacuum hose out of mount. (green arrow)

Working at front of air filter housing, using a flathead screwdriver loosen air duct hose clamp.
Figure 9

Working at front of air filter housing, using a flathead screwdriver loosen air duct hose clamp. (green arrow) Then loosen boost pipe hose clamp (yellow arrow). Leave boost hose connected for now.

Once hose clamp is loose, reach below upper radiator hose and slide hose (green arrow) off air filter housing.
Figure 10

Once hose clamp is loose, reach below upper radiator hose and slide hose (green arrow) off air filter housing.

Working at rear of air filter housing, using a flathead screwdriver loosen air duct hose clamp.
Figure 11

Working at rear of air filter housing, using a flathead screwdriver loosen air duct hose clamp. (green arrow) Next you will have to detach electrical cables from intake air pipe. (yellow arrow)

Pull electrical cable up off mount.
Figure 12

Pull electrical cable up off mount. You may have to wiggle the rubber grommet side to side to get it to come off mount. Remove all three electrical cables.

Once the electrical cables are removed, you will have to pull the air filter up and out of the rubber mounting grommets.
Figure 13

Once the electrical cables are removed, you will have to pull the air filter up and out of the rubber mounting grommets. There are two in the back and one located in the center. What I like to do is pull the front side up first, then wiggle the air filter housing until it comes out of the rear mounts. There are no fasteners holding it, just the grommets, and over time they may become stiff and will not release easily. If that is the case use caution and pull up swiftly to release.

Next you will have to unlock and disconnect the front boost recirculation hose.
Figure 14

Next you will have to unlock and disconnect the front boost recirculation hose. There is a gray lock, rotate this lock counterclockwise about 45° to unlock it. (green arrow). This style hose lock can be hard to get off due to time and debris entering collar. If so, you can rotate it using channel locks, but be careful not to damage the hose or lock, they are made out of plastic.

Next, pull hose up and off air pipe.
Figure 15

Next, pull hose up and off air pipe. It should slide off easily, if it does not, lock is not fully disengaged.

Next you will have to unlock and disconnect the rear boost recirculation hose.
Figure 16

Next you will have to unlock and disconnect the rear boost recirculation hose. There is a gray lock, rotate this lock counterclockwise about 45° to unlock it. This style hose lock can be hard to get off due to time and debris entering collar. If so, you can rotate it using channel locks, but be careful not to damage the hose or lock, they are made out of plastic. Next, pull hose up and off air pipe. It should slide off easily, if it does not, lock is not fully disengaged.

Working at the boost recirculation valves, remove the vacuum hose from each valve by pulling off.
Figure 17

Working at the boost recirculation valves, remove the vacuum hose from each valve by pulling off. Be careful not to damage hose or valve when removing.

Working at the boost air pipe, remove T27 Torx fastener.
Figure 18

Working at the boost air pipe, remove T27 Torx fastener. (green arrow)

Working at throttle body, using a flathead screwdriver, remove intake air pipe locking clip.
Figure 19

Working at throttle body, using a flathead screwdriver, remove intake air pipe locking clip. (green arrow)

Disconnect boost pipe from connection at radiator support, then gently wiggle pipe off throttle body.
Figure 20

Disconnect boost pipe from connection at radiator support, then gently wiggle pipe off throttle body.

Working at front of alternator, remove idler pulley cap using a flathead screwdriver, then remove 16mm mounting bolt and remove idler pulley from alternator.
Figure 21

Once pipe is clear of throttle body, remove from vehicle.

All E90 Models
Working at rear of alternator, disconnect electrical connector by pressing release tab and pulling off.
Figure 22

Working at front of alternator, remove idler pulley cap using a flathead screwdriver, then remove 16mm mounting bolt and remove idler pulley from alternator. (green arrow)

Remove four E12 alternator fasteners.
Figure 23

Working at rear of alternator, disconnect electrical connector by pressing release tab and pulling off. (green arrow). Then remove positive battery cable 13mm mounting nut (yellow arrow).

Next remove alternator from mounting bracket by lifting up and off bracket.
Figure 24

Remove four E12 alternator fasteners. (green arrows)

25
Figure 25

Next remove alternator from mounting bracket by lifting up and off bracket. To install new alternator, reverse removal steps. Check operation of charging system and alignment of drive belts.

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Comments and Suggestions:
Steve Comments: Hi. Do you have the part number for the two screws at the green arrows in Figure 1? I also need the number for the two push fasteners at the lower corners of that same trim panel, which can also be seen in Figure 1. A previous mechanic played fast and loose with a lot of underhood fasteners. Thank you.
November 28, 2016
  Followup from the Pelican Staff: I’m not the best with part numbers.


Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
F355Driver Comments: I answered my own question. Yes the alternator can be opened while it is still in the car and you can replace the voltage regulator BOSCH F00M346033 or equivalent and the rectifier. The rectifier is part of the rear housing, but it can be removed. I don't have the rectifier part number though. I am replacing the voltage regulator because I was seeing 15.1V at the terminals with the car running and it should be below 14.6V.
February 13, 2016
  Followup from the Pelican Staff: Thanks for the additional info and feedback. We appreciate it.
- Nick at Pelican Parts
 
F355Driver Comments: My 2007 BMW 335i is having electrical issues, so I am going to check the alternator. One quick question, is it possible to rebuild the alternator without removing it. It looks like I can just remove the screws from the back and pull the cover to get access to the regulator and rectifier.
February 13, 2016
  Followup from the Pelican Staff: I am not aware of any rebuild kits. Give our parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
James Comments: After reinstalling the new alternator, i have put the belt back onto the alternator pulley. Do i still adjust the tension of the belt using the T60 torx on the belt tensioner?

January 17, 2016
  Followup from the Pelican Staff: What type of vehicle? Om E90 models the tensioner is automatic, no adjustment needed. - Nick at Pelican Parts  
Erik Comments: is the one pictured a bosch or valeo? mine looks like tdc6's picture. thanks
September 19, 2015
  Followup from the Pelican Staff: I am not 100%, don't recall. If you use the last 7 of your VIN and call our parts specialists, they can help. Give our parts specialists a call at 1-888-280-7799.
- Nick at Pelican Parts
 
ASOGAN Comments: ALTERNATOR AND BATTERY HAVE BEEN CHECKED FOR VOLTAGE.ALL IS GOOD BUT SEEMS CAR IS NOT RECOGNIZING ALTERNATOR AND HENCE NOT CHARGING BATTERY.THEY THINK IT COULD BE DME CONTROL UNIT.
July 23, 2015
  Followup from the Pelican Staff: If voltage is good, the vehicle would be charging, right? I would check charging system voltage and current, voltage drop test the battery cables and check DME alternator control. - Nick at Pelican Parts  
asogan Comments: HI my alternator was replaced but still not charging battery.Instrument cluster lights up with all sorts of warning lights.Advice please.Car is a 2008 bmw 320i auto
July 21, 2015
  Followup from the Pelican Staff: Does the alternator have power at the main connection? What is charging voltage and current?- Nick at Pelican Parts  
Gallobmw Comments: I have the same problem on a 2007 335 e92 I don't have enough room to pull the alternator out. Do I have to remove the oil filter housing? Anybody have any tips or ideas.
July 13, 2015
  Followup from the Pelican Staff: See this comment Lombardispot Comments: There was a previous comment that the oil filter housing needed to come off. I also nearly thought this was necessary, even with trying to rotate. As it turned out, there are two things that made it possible to rotate it out.
1. Take off the idler pulley because it prevents the alternator from rotating.
2. Use a rubber mallet. A few taps from a rubber mallet help get the alternator rotating past the sticking points.- Nick at Pelican Parts
 
Muaz Comments: Hi I'm trying to remove my alternator on my 335i, but I can't find the three bolts holding the ac bracket. Can you help me out thanks
June 24, 2015
  Followup from the Pelican Staff: The fasteners for the bracket are behind the compressor. The compressor has to be removed first. Do not remove the refrigerant lines without discharging the refrigerant system first. - Nick at Pelican Parts  
Lombardispot Comments: There was a previous comment that the oil filter housing needed to come off. I also nearly thought this was necessary, even with trying to rotate. As it turned out, there are two things that made it possible to rotate it out.
1. Take off the idler pulley because it prevents the alternator from rotating.
2. Use a rubber mallet. A few taps from a rubber mallet help get the alternator rotating past the sticking points.
June 13, 2015
  Followup from the Pelican Staff: Thanks for sharing your installation process and experience. These type of comments add so much to the Pelican tech community.
- Nick at Pelican Parts
 
Lombardispot Comments: Is it really necessary to remove the fan? The photos show nearly everything coming out far from the fan. Why does the fan need to come out?
June 8, 2015
  Followup from the Pelican Staff: BMW recommends removing the cooling fan. It allows room during the repair. - Nick at Pelican Parts  
maxl1961 Comments: For my 2009 335 XDrive, I couldn't remove the alternator without remove the oil filter housing. I have to remove:
1. Electric Fan assembly 2 screws, 1 is on top, 1 is on the bottom.
2. Drain coolant. Remove the oil in the oil filter housing.
3. Disconnect the coolant hose to the filter housing.
4. Remove the oil filter housing. Be very careful to use star wrench to remove 3 different length of screws.
5. Now, you should have enough room to work with. There is no short cut for me.
4.
May 21, 2015
  Followup from the Pelican Staff: Thanks for sharing your installation process and experience. These type of comments add so much to the Pelican tech community.
- Nick at Pelican Parts
 
tdc6 Comments: I have a 2008 335i and I followed your instructions to remove my alternator. Everything went well until the last step: removing the alternator. There is no room to "lift up and remove the alternator". Either the oil filter housing or the bottom bracket must be removed. Very frustrating.
May 20, 2015
  Followup from the Pelican Staff: It should lift out. Try rotating it as you lift so the mounting bores clear the obstructions. - Nick at Pelican Parts  
Jr Comments: Thank you both for very helpful comments! I was able to properly diagnose alternator with trick mentioned above. Helped me confirm what I thought was the problem alternator. This website is great!
December 22, 2014
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
Fairfield Imports Pensacola FL Comments: Before you replace this alternator test the over run pulley. Most of these alternators are being replaced due to the pulley. Remove the belt from the alternator and insert a screwdriver into the front of the alternator. You want it to hold it from spinning. The pulley should act like a ratchet and only turn in one direction. If it is frozen you will likely have to replace the alternator. If it free spins just change out the pulley. If the alternator is making a bad bearing noise remove the pulley and check the alternator. Odds are good it is the pulley. You can get these pulleys from the dealer but they have to special order them. You will also need a special tool to remove it. Most auto parts stores have them.
November 3, 2013
  Followup from the Pelican Staff: Thanks for the additional Info. We appreciate it.
- Nick at Pelican Parts
 
Greg Comments: Nice write up. It would be helpful if the instructions included information on the the Aluminum E12 Bolts used to attach the alternator. Per BMW NA, these are one use bolts and should be replaced with new when replaceing the alternator Part # 12310392568. Also, having the proper torque settings listed for these as well as the idler pulley mounted on the front of the alternator would be a useful addition.
September 17, 2013
  Followup from the Pelican Staff: Thanks for the input on this one, we missed the bolts in this article. We'll add a note and the parts information. We appreciate the help. - Nick at Pelican Parts  

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