Main generator faults (VW Passat B5)

Cause	Method of elimination
When the ignition is turned on, the battery charging indicator light does not light
The battery is discharged	Check the voltage and charge the battery if necessary.
Poor connection or oxidation of battery terminals	Check the connection for reliability and clean the battery terminals if necessary.
The wire on the generator contact is not tightened securely or is oxidized	Check and, if necessary, tighten the generator mounting wire.
The control light has burned out	Replace the light bulb.
The voltage regulator is faulty	Check and replace the voltage regulator if necessary.
Broken wire between generator, ignition switch and indicator lamp	Check the voltage along the circuit starting from the generator.
Generator brushes do not fit tightly against the slip rings	Check the length of the brushes and their freedom of movement in the holders.
The generator excitation winding burned out	Check the rotor and diodes, which must be replaced if defects are found.
Battery charge indicator light does not go out when engine speed increases
The poly V-belt is not sufficiently tensioned or is worn out	Check the condition of the poly V-belt and belt tensioner mechanism.
Idle clutch faulty (tDI only)	Remove the alternator and turn the alternator shaft counterclockwise. If the movable surface of the belt pulley does not turn, the idle clutch is faulty.
The voltage regulator or generator is faulty	Disconnect the (D+) wire from the rear of the alternator and turn on the ignition. If the test light still does not light, the alternator or voltage regulator is faulty.
The voltage regulator brushes are worn out	Check the length of the brushes and replace them if necessary.
The voltage regulator is faulty	Check the voltage regulator and replace it if necessary.
Generator faulty	Check the generator and replace it if necessary.
Defective wire connecting the generator to the voltage regulator	Disconnect the blue wire in the T32A electrical connector of the junction box block 12. If after this the test lamp does not light, then the D+ wire is shorted to ground and the wire must be replaced.
The distribution box is faulty	Disconnect the blue wire from the T32A electrical connector. If the indicator lamp lights up after this, the junction box is faulty.
The battery charge indicator light is on when the ignition is off
Diode short circuit	Check and replace the diode if necessary.