Preparing for the test
Before starting the test, perform the following checks and repair if necessary:
Check that the battery installed in the vehicle is in good condition. The procedure for checking the battery is provided in the section "Battery".
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.
Check the tension of the alternator drive belt.
Turn the ignition key to the "OFF" position.
Disconnect the cable from the (-) terminal of the battery.
Disconnect the standard wire from the generator terminal "B".
Connect an ammeter (DC, 0-100A range) in series between the alternator terminal "B" and its standard wire. Make sure that the (-) wire of the ammeter is connected to the standard wire disconnected from the alternator.
Note: Make sure each connection is secure and tight, as the terminals will carry a large amount of current. Do not use clips (alligator clips) when connecting to an electrical circuit.
Connect a voltmeter (0-20V scale) between the alternator "B" terminal and ground. Connect the (+) lead of the voltmeter to the alternator "B" terminal, and then the (-) lead of the voltmeter to a suitable ground (the body).
Fig. 7.20. Generator output current test circuit
Connect the test tachometer according to the manufacturer's instructions. Connect the wire to the (–) terminal of the battery (Fig. 7.20).
Leave the engine hood open.
Verification procedure
Make sure the voltmeter shows battery voltage. If the voltmeter shows 0 V, there is an open circuit between the alternator "B" terminal and the (-) battery terminal. Check for a blown fuse or poor ground connection.
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).
Note: After the engine starts, the generator output current drops quickly. Perform the test as quickly as possible to measure the maximum output current.
Analysis of results
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.
Maximum allowable value: generator 95 A, minimum 63.0 A.
Note: The generator's rated output is stamped on a plate attached to the generator housing.
Note: The output current varies depending on the generator load and the generator case temperature. Therefore, the rated output current may not be achieved. In such cases, turn on the high beam headlights for a while or connect the outside lighting system of another vehicle to increase the electrical load (in order to discharge the battery). The rated output current of the generator may not be achieved due to overheating of the generator case or excessively high ambient temperature. In such cases, allow the generator to cool down, and then recheck.
After completing the generator output current test, gradually reduce the engine speed to idle speed, then turn the ignition switch to the "OFF" position.
Disconnect the wire from the (–) terminal of the battery.
Remove the ammeter, voltmeter and control tachometer.
Connect the standard wire to the "B" terminal of the generator.
Connect the wire to the (–) terminal of the battery.