1. Before starting the test, check:
- installation of a generator;
- alternator drive belt tension;
- fusible link;
- absence of extraneous noise from the generator when the engine is running.
2. Turn the ignition key to the "OFF" position.
3. Disconnect the cable from the negative terminal of the battery.
Fig. 9.1. Generator output voltage drop test diagram: 1 – generator; 2 – terminal "B"; 3 – voltmeter; 4 – ammeter; 5 – battery
4. Disconnect the wire from the "B" terminal of the generator and connect an ammeter (DC) with a range of 0–100 A in series between the "B" terminal and the wire disconnected from the generator (connect the wire from the "+" ammeter to the "B" terminal of the generator, and then the wire from the "–" ammeter to the wire disconnected from the generator) (Fig. 9.1).
Attention! It is recommended to use an ammeter with an inductive sensor ("current clamp"), which allows you to measure the current without disconnecting the wire from the "B" terminal of the generator. Using this type of ammeter allows you to reduce the possible voltage drop due to poor contact of the wire with the "B" terminal of the generator.
5. Connect a digital voltmeter to the "B" terminal of the generator and the positive terminal of the battery (connect the "+" wire of the voltmeter to the "B" terminal of the generator, and the "–" wire of the voltmeter to the "+" terminal of the battery).
6. Connect the tachometer.
7. Reconnect the cable to the negative battery terminal.
8. Leave the car hood open.
9. Start the engine.
10. Maintaining the engine speed at 2500 min⁻¹, turn the headlights and exterior lights on and off, thereby adjusting the load on the generator so that the output current (shown on the ammeter) is slightly higher than 30 A.
11. Gradually reduce the engine crankshaft speed until the current on the ammeter is 30 A. At the same time, read the voltmeter readings.
The maximum permissible voltage drop value is 0.3 V.
Caution: If the generator output is high and you cannot reduce the ammeter reading to 30 A by turning on the load, set the current value to 40 A. Take the voltmeter readings for this case.
12. If the voltmeter readings exceed the maximum permissible value, there is probably a fault in the circuit coming from the generator terminal "B". In this case, you should check the circuits between the generator terminal "B" and the positive terminal of the storage battery (including the fuse link).
13. If the wire connection to the generator terminal has become loose or the wire insulation in the harness has changed color due to overheating, then fix the problem and recheck.
14. After checking, let the engine idle.
15. Turn off all external lights and ignition.
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16. Disconnect the cable from the negative terminal of the battery.
17. Disconnect the ammeter, voltmeter and tachometer.
18. Connect the standard wire to the generator terminal "B".
19. Connect the cable to the negative terminal of the battery.