Checking and replacing generator brushes (BMW 5 Series E28)

If your vehicle's radio has an anti-theft system, make sure you know the correct activation code before disconnecting the battery. Refer to Section 1 for information before disconnecting the wire Anti-theft audio system and instrument cluster language.

If a message in another language appears on the instrument cluster display after connecting the battery, refer to Section 1 for the language setting procedure Anti-theft audio system and instrument cluster language.

Disconnect the negative battery cable.

Bosch Generator

1. Remove the voltage regulator from the rear of the generator (see section Replacing the voltage regulator).



2. Measure the length of the brushes. They should not be shorter than 6 mm. If any of them are worn to this limit, replace the entire set.

3. Also check for wear on the collector ring (see illustration).

4. The brushes are either screwed or soldered. If you are not experienced in soldering, it may be better to have an electrician install the brushes.

Be careful not to heat the soldering area for more than 5 seconds. If necessary, use a heat sink to prevent overheating. This can be done with narrow pliers, which should be grasped near the soldering area.

5. For screw mounting, hold the assembly in place and install the screws. Tighten the screws gradually and evenly to prevent the holder from warping.

6. Install the voltage regulator assembly onto the generator.

7. Connect the negative battery cable.

Motorola Generator

1. Remove the generator.

2. The brushes are mounted under the voltage regulator at the rear of the generator (see illustration).

3. Remove the mounting screws and insulating washers and separate the voltage regulator and brush holder from the housing on the collector side.

4. Measure the length of the brushes (see the illustration above). If any of the brushes are shorter than 6mm, replace the entire set.

5. Make sure that the brushes move without jamming in the brush holder.

6. Install the brush holder/voltage regulator. Tighten the screws securely. Make sure the brushes are not shorted to ground.

7. Installation is the reverse of removal.