Before performing a test, always check the following:
- installation of the generator and connection of wires;
- battery;
- alternator drive belt tension;
- fusible link;
- absence of extraneous noise from the generator when the engine is running.
Note: The battery used for this test must be slightly discharged. The load of a fully charged battery is not suitable for performing this test accurately.
Turn the ignition key to the "OFF" position.
Disconnect the cable from the (-) terminal of the battery.
Fig. 7.23. Generator output current test circuit
Disconnect the standard wire from the "B" terminal of the generator. Connect an ammeter (DC, with a range of 0-100 A) in series between the "B" terminal and the standard wire disconnected from the generator. Connect the (+) wire of the ammeter to the "B" terminal of the generator, and then the (-) wire of the ammeter to the standard wire disconnected from the generator (Fig. 7.23).
Warning! Do not use clamps (crocodile clips) when connecting to an electrical circuit. Tighten the connections with bolts and nuts. Otherwise, a bad connection (using crocodile clips) may cause a serious malfunction (or even an accident) due to high current.
Note: We recommend using an ammeter with an inductive type sensor ("current clamp"), which allows you to measure current without disconnecting the standard wire from the generator.
Connect a voltmeter (0-20V scale) between the alternator "B" terminal and ground. (Connect the (+) lead of the voltmeter to the alternator "B" terminal, then the (-) lead of the voltmeter to ground.)
Connect a test tachometer or tester.
Connect the wire to the (–) terminal of the battery.
Leave the engine hood open.
Check that the voltage shown by the voltmeter is equal to the battery voltage.
Note: If the voltmeter shows 0 V, then either there is a break or the fuse has burned out in the circuit between the generator terminal "B" and the (+) terminal of the battery.
Start the engine and turn on the headlights.
Turn on the high beam headlights and set the heater electric fan switch to the "HIGH" position, then sharply increase the engine speed to 2500 min⁻¹ and read the maximum value of the generator output current (shown by the ammeter).
Maximum permissible value: 70% of the rated output current.
Note: The rated output current is specified in table 7.1.
Since after starting the engine the current generated by the battery drops quickly, the procedure for increasing the engine speed must be performed as quickly as possible in order to have time to measure the maximum value of the generator output current.
The magnitude of the output current will depend on the electrical load and the temperature of the generator housing.
If the electrical load is low during the test, the specified generator output current will not be achieved, even though the generator is in good working order.
In such cases, to increase the electrical load (in order to discharge the battery), turn on the high beam headlights for a while with the engine off, and then perform the test again.
The specified value of the generator output current may not be obtained also due to overheating of the generator housing or at too high ambient air temperature. In such cases, let the generator cool down and perform the test again.
The ammeter readings should be above the maximum permissible value. If the ammeter readings are below the maximum permissible value, and the generator terminal "B" circuit is in good condition, remove the generator from the car and test it on a bench.
After checking, let the engine idle.
Turn the ignition key to the "OFF" position.
Disconnect the test tachometer or tester.
Disconnect the wire from the (–) terminal of the battery.
Remove the ammeter and voltmeter.
Connect the standard wire to the "B" terminal of the generator.
Connect the wire to the (–) terminal of the battery.