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BMW – Replacing An Alternator DIY- 2001 325i – E46 M54

November 27, 2009

While replacing an alternator may sound intimidating, this is a repair that you can perform on your own and save a bundle in labor charges. You will likely be quoted anywhere from $150 to a few hundred dollars in labor for an alternator replacement. In your own garage (or driveway), you can replace your alternator in as little as an hour (in most cases) using standard automotive metric tools.

Come along as we replace the alternator in our 2001 325xi. The procedure will be similar on most 6-cylinder and 4-cylinder models. (Alternator replacement on V8 and V12 BMWs is more involved.) As always, the full procedure for your particular BMW or MINI will be detailed in the applicable Bentley or Haynes repair manual. We have all the manuals in-stock, as well as the special fan clutch wrench and the fan pulley holder tool, shown in this procedure.

1 – Disconnect the negative battery cable at the battery (in the trunk on most models, some under rear seat or under the hood). On early models (most pre-1999) we recommend getting the Memory Saver (part #295A) and a 9-volt battery to prevent the loss of computer and radio codes.

2 – Remove air filter box:


Loosen the hose clamp securing the rubber intake boot to the Mass Air Flow sensor (MAF)


Pull the boot back off of the flange on the MAF (Fig. 2).

Unplug the harness plug from the MAF. Remove the two 10mm bolts from the air filter box mounting flange (Fig. 3).


Pull the box up from the rear and out (Fig. 4).

3 – Remove cold-air snorkel:


Pry up the center pin on the three plastic securing rivets, then pull the rivet assemblies out (Fig. 5).


Lift out the snorkel assembly (Fig. 6).

4 – Remove cooling fan and shroud (Note: this is only required if the belt and/or idler pulleys are to be replaced, which we highly recommend while you’re in there.):


Unclip and remove the AUC (automatic air quality sensor) module from the fan shroud and set off to the side (Fig. 7).


Remove the auxiliary fan harness connector assembly from the fan shroud and set off to the side (Fig. 8).


Remove the plastic rivet (similar to those in step 2) on the driver side and the Allen screw on the passenger side that secure the fan shroud to the radiator. Remove the engine fan using the 32mm wrench and the fan pulley holder tool. Figure 9 shows how the tools are used. (The fan and shroud are removed for this photo to better illustrate how the tools are used.)


Figure 10shows the tools in actual use. Note that the 32mm fan clutch nut is left-hand thread; in other words, the wrench will turn clockwise (when viewed from the front). Use a hammer to give the end of the wrench a quick blow to loosen the nut, then just spin the fan to finish removing the assembly


.Once the fan is free, pull the fan and the shroud up and out (Fig. 11)

5 – Remove accessory drive belt


Use a socket and ratchet on the tensioner hex-lug to relieve tension on the belt tensioner and pull the belt off of the alternator pulley (Fig. 12).

6 – Remove the alternator electrical connectors:


Remove the nut securing the main positive cable (Fig. 13 )


and pull the cable from the stud. Release the clip and pull the control harness plug from the rear of the alternator (Fig. 13).

7 – Remove power steering fluid reservoir:


Remove the two bolts securing the reservoir to the engine (Fig. 14) and set the reservoir over to the driver side, out of the way.

8 – Remove Alternator:


Remove the upper and lower alternator mounting bolts (Fig. 15).

Take a look at the new alternator to help you locate where the bolts should be. Lift alternator out. You may have to gently use a pry bar to initially work the alternator off the mounting brackets.

9 – If necessary, install the pulley from the old alternator, then install the new alternator.

10 – If installing new belts and tensioner pulleys, do so at this time.

11 – Install the remainder of the parts in the reverse order. When installation is complete, re-connect the battery cable.

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  1. Good morning. Step #8 is intuitive however, for novice do-it-yourself owners there should be some description of which bolts to remove since some individuals tend to follow instructions on a step-by-step basis. There maybe some realstate issues however. Thnx so much of the issue. Big help and big savings and more thorough job is done.

    • Thank you for your comments. Since there are differing alternators and mounting, through the various models, the best source for model specific details would be the Bentley repair manuals (see links in the main post).

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