Charging System: Testing and Inspection
Generator not charging- Generator belt slack
- Charging circuit and/or ground circuit open
- Brushes defective
- Voltage regulator defective
- Diodes defective
- Excitation circuit open
- Rotor winding open-circuited
- Stator grounded
Insufficient or Irregular output current
- Generator belt slack
- Brushes defective
- Voltage regulator defective
- Rectifier diodes defective
- Rotor partially short-circuited
- Open circuit or partial short circuit in stator connection to ground
Current too high
- Voltage regulator defective
- Poor contact between voltage regulator and generator
Generator noisy
- Generator belt extremely worn
- Belt pulley incorrectly installed
- Generator insecurely mounted
- Generator and crankshaft pulleys misaligned
- Bearings worn or defective
- Rectifier diode short-circuited
Basic checks
WARNING : Never start the engine while carrying out this checking procedure as the generator will be irreparably damaged.
1 If the lamp does not light up when the ignition is switched on, ground the D+ terminal on the generator while the ignition is still switched on.
2 If the lamp lights up, the electrical system is OK and the generator is at fault.
Checking generator output voltage
1 Connect a voltmeter to the battery terminals.
2 Run the engine at medium-high revs for several minutes and note the voltmeter reading.
A reading of about 13.5 - 14 V should be obtained.
Checking maximum generator output power
1 Connect an ammeter to the generator's output circuit (B+) or use a clip-on ammeter.
Run the engine at about 2500 rpm.
2 Apply a maximal electrical load to the generator, either by connecting a special carbon-film resistor to it or by switching on all the car's items of electrical equipment.
Note the instrument reading.
3 The ammeter reading out to be the same as the generator's nominal rating
Checking the voltage drop at the positive and negative generator terminals
1 Connect a voltmeter to the positive battery terminal and terminal B+ on the generator (insulated side).
2 Run the engine at 2500 rpm and load the generator by switching on all the lights, for instance.
Note the instrument reading.
3 Connect a voltmeter to the negative battery terminal and terminal B- (ground) on the generator.
4 Run the engine at 2500 rpm and load the generator by switching on all the lights, for instance.
Note the instrument reading.
5 The readings in points 2 and 4 should not exceed 0.5 V.
If a higher reading is obtained, check the relevant circuit for shorting/continuity.