DESCRIPTION
All models are equipped with Bosch 3-phase, self-rectifying, 110-amp generator. (Scheme 1) This internally-regulated generator is equipped with 14 diodes, with 3 exciter diodes connected to stator windings. These diodes turn off the generator indicator light and supply power to the voltage regulator while the engine is running.
Exploded View Of Bosch 110-Amp Generator. Scheme 1
BELT TENSION
Engines are equipped with serpentine belt. Belt adjustment is not necessary.
Generator Exciter Circuit Tests (Current Test)
Ensure battery voltage is at least 12 volts. Disconnect Blue (D+) wire from generator. Connect digital ammeter between generator Blue wire terminal and Blue wire. Set digital ammeter to 200-mA range. Turn ignition on. If amperage is not 150-185 mA (milliamps), check Blue wire between generator and instrument panel, and check instrument cluster printed circuit.
Generator Exciter Circuit Tests (Resistance Test)
Disconnect negative battery cable. Disconnect Blue (D+) wire from generator. Connect ohmmeter leads between Blue wire and battery positive terminal. Turn ignition on. Resistance should be 140-160 ohms. If resistance is not 140-160 ohms, check generator bulb. If bulb is okay, replace instrument cluster printed circuit and retest.
Generator Output Test
- Ensure connections at battery, generator and starter are clean and tight. Ensure generator, engine and body are properly grounded. Ensure drive belt is adjusted and in good condition.
- Connect Ammeter/Voltmeter Tester (VAT-40/60 ) according to manufacturer's instructions. Operate engine at 2000 RPM. Generator output should be 90-110 amps.
- If generator output is low, repair or replace generator. If reading is 16-20 amps less than generator rating, replace regulator. If output is still low, repair or replace generator.
Diode Assembly
- Set ohmmeter on 100x scale. Connect ohmmeter leads between generator output terminal and each of 3 stator terminals in turn. (Scheme 2) Reverse ohmmeter leads. If ohmmeter indicates continuity in only one direction, go to next step. If ohmmeter indicates continuity in both directions, replace diode assembly.
- Connect ohmmeter leads between negative plate and each of 3 stator terminals in turn. Reverse ohmmeter leads. If ohmmeter indicates continuity in only one direction, go to next step. If ohmmeter indicates continuity in both directions, replace diode assembly.
- Connect ohmmeter leads between Blue (D+) wire terminal and each of 3 stator terminals in turn. Reverse ohmmeter leads. If ohmmeter indicates continuity in only one direction, diode assembly is okay. If ohmmeter indicates continuity in both directions, replace diode assembly.
Testing Diode Assembly (Bosch 110-Amp Generator). Scheme 2
Stator
- Set ohmmeter on lowest scale. Connect ohmmeter leads between stator leads. If resistance is not about .09-.10 ohm, stator windings are open or shorted. Replace stator.
- Set ohmmeter on 1000x scale. Connect ohmmeter leads between stator core and stator lead. If continuity exists, stator is grounded. Replace stator.
Rotor
- Set ohmmeter on lowest scale. Connect ohmmeter leads between slip rings. If resistance is less than 2.8 ohms, rotor windings are shorted. Replace rotor. If resistance is greater than 3.1 ohms, high resistance exists in rotor windings. Replace rotor.
- Set ohmmeter on 1000x scale. Connect ohmmeter leads between either slip ring and rotor. If continuity exists, rotor is grounded. Replace rotor.
- Clean slip rings using fine sandpaper. If rings are worn or pitted, turn them on lathe. Minimum slip ring diameter is 1 1/16" (27 mm).
- If slip rings cannot be repaired, remove rear bearing from slip ring end of rotor. Unsolder wires from slip rings. Bend up ends of rotor winding. Pull off slip rings. Ensure ends of rotor winding are not damaged.
- Insert ends of rotor winding into slip ring, and press new slip ring onto rotor until slip ring end is 9/64" (3.57 mm) from end of collar. Solder rotor winding to slip ring terminals. Turn rings on lathe, and retest rotor. Maximum slip ring runout is .0012" (.03 mm).
Brushes
Ensure new brushes are .47" (12 mm) long. Used brushes must be at least .16" (4 mm) long.
TROUBLE SHOOTING
Note. For additional trouble shooting, see the TROUBLE SHOOTING - BASIC PROCEDURES article in the GENERAL INFORMATION section.
Light Does Not Come On With Ignition On & Engine Off
- Disconnect Blue (D+) wire from generator. Connect jumper wire between Blue wire and ground. Turn ignition on. If indicator light does not come on, go to step 3). If indicator light comes on, go to next step.
- Check for poor generator ground and worn brushes. If generator ground and brushes are okay, replace voltage regulator. If light still does not come on, replace generator.
- Disconnect negative battery cable. Replace indicator light bulb and reconnect negative battery cable. If indicator light still does not come on, repair circuit between generator and indicator light.
Light Remains On When Ignition Is Off
Defective generator diode and/or rectifier bridge. Replace generator.
Light Does Not Go Out When Engine RPM Is Increased
- Check drive belt tension. If tension is okay, disconnect Blue (D+) wire from generator. Turn ignition on.
- If indicator light does not come on, perform «GENERATOR OUTPUT TEST»(/audi/a4/b5-1994-1999/remont/charging-system/#alternator-regulator__generator-output-test) under ON-VEHICLE TESTING. If indicator light comes on, check for short to ground in Blue wire between generator and indicator light. If Blue wire is not shorted to ground, replace generator.
Removal & Installation
Removal and installation is basically an unbolt and bolt-on procedure. Tighten upper generator bolt to 33 ft. lbs. (45 N.m) and lower bolt to 18 ft. lbs. (25 N.m).
OVERHAUL
Note. See exploded view of generator. (Scheme 1)
