Repairing alternator (90 A Bosch version) — VW

From October 1982

O-ring
Lubricate with multi-purpose grease

Bearing (slip ring end)
Removing with parting tool, e.g. Kukko 15/0 or 17/0 and puller e.g. Kukko 18/0
Installing: press inner race in fully

Note:

Always use a new bearing: Do not damage slip ring.

Rotor
Checking => figs.
1
,
2

Voltage regulator/carbon brushes
Removing: can be done without taking generator off
Carbon brush wear limit = 5 mm

Note:

Supplied together as service part.

8 Nm
Suppression condenser
Housing
Mark position in relation to end plate

Diode plate
Removing and installing: use long nosed pliers to dissipate heat at soldered points: use max: 300 W soldering iron. If diodes are faulty, renew complete
Checking => fig.
5

Stator
Removing and installing: Use long nosed pliers to dissipate heat at soldered points. Use max. 300 W soldering iron
Checking => figs.
3
,
4

40 Nm
Pulley
Diameter 61 mm

End plate
Mark position in relation to housing

Spacer
Removing: with parting tool, e.g. Kukko 15/0 or 17/0 and puller e.g. Kukko 18/0

Bearing (drive end)
Removing: with parting tool, e.g. Kukko 15/1 or 17/1 and puller e.g. Kukko 18/0
Installing: press inner race in fully

Note:

Always use a new bearing

Fig.1
Checking rotor/earth short

Tester: V.A.G 1315 A

Press button for resistance measurement. A flashing resistance value must be indicated in the KOhm range.

Fig.2
Checking rotor/winding short or open circuit

Tester: V.A.G 1315 A

Press button for resistance measurement. Specified reading 90 A alternator: 2.8 - 3.0 Ohm.
Open circuit if a flashing resistance value is indicated in the KOhm range. Winding short if resistance is below specified reading.

Fig.3
Stator/checking for short to earth

Tester: V.A.G 1315 A

Press button for resistance measurement.
Connect test leads to measuring points 1 and 2; 1 and 3; 1 and 4; 1 and 5. A flashing resistance value must be indicated in the KOhm range.

Fig.4
Stator/checking for open circuit

Tester: V.A.G 1315 A

Press button for resistance measurement.
Apply test probes to winding ends 1 and 2; 1 and 3; 1 and 4; 2 and 3; 2 and 4; 3 and 4 one after the other. At each point the reading must be 0 Ohm.
There is an open circuit if a flashing resistance value is indicated in KOhm range at one of the test points.

Fig.5
Checking diode plate

Unsolder stator windings.

Tester V.A.G 1315 A

Press buttons for resistance and voltage test at same time:
Checking plus diodes: Black clip on plus heat sind -1- (B+)and red clip to collection points -2- one after the other.
Checking minus diodes: Red clip on minus heat sink -3- and black clip to collection points -2- one after the other.
Checking exciter diodes: Black clip on -4- (D+) and red clip to collection points -2- one after the other.

The reading for all tests must be 3 times 50 - 80 Ohm. If this is not the case, renew the diode plate.