BMW X3 2005



Diagnosis & Testing

The alternator provides power consuming components with current while the engine is running and maintains battery charge. The alternator is mounted on the front edge of the engine. The output of the alternator depends on engine speed. When the engine is idling, the alternator operates at approximately half of maximum output. When the engine is idling with many power consuming components engaged, the alternator may be unable to maintain full battery charge.

The alternator creates an alternating current which is converted to a direct current in the rectifier bridge. The alternator also utilizes a built-in voltage regulator.

  1. Check that the wiring is in good condition.
  3. Check for any abnormal noise from the alternator while the engine is running.
  5. Check the accessory drive belt for wear or slippage.
    With the engine running at 2500 RPM, headlights on and fan blower on high, the alternator output voltage should be 13.9-14.6 volts at 68°F.


Removal & Installation

When the battery is disconnected the radio code, on-board computer and clock settings will be lost. The radio code should be obtained before disconnecting the battery or radio. Once the battery has been reconnected, the radio will not function unless the code is keyed in.

  1. Read out stored fault codes (if applicable).
  3. Switch off ignition.
  5. Disconnect negative battery cable.
  7. Remove or disconnect the following:

    Suction filter housing
    Fan clutch
    Alternator drive belt
    Power steering pump from mounting (move aside)
    Alternator air hose (if equipped)
    Electrical connections from alternator
    Alternator mounting bolts (versions without idler pulley)

    Click image to see an enlarged view

    Fig. Showing idler pulley bolt and alternator bolt (3.0L engines)

    Idler pulley cover and idler pulley bolt (versions with idler pulley)


To install:

  1. To install, reverse removal procedure.
  3. If equipped with idler pulley, turn lock of tensioning roller to engage alternator groove.
  5. With scan tool, clear fault code memory.