Charging System Inspection - Generator Output Current Test

This test determines whether the generator output current meets the rated value.

PREPARATION FOR INSPECTION

1. Before starting the test, perform the following checks and repair as necessary:

1) Check the condition of the battery installed in the vehicle. Refer to the "Battery" section.

The battery used for this test should be slightly discharged. A load created by a fully charged battery is not suitable for an accurate test.

2) Check the tension of the generator drive belt.

Refer to the "COOLING SYSTEM" section.

2. Turn the ignition switch to the "OFF" position.

3. Disconnect the wire from the negative (-) battery terminal.

4. Disconnect the original wire from the generator "B" terminal.

5. Connect a DC ammeter (range 0–100 A) in series between the generator "B" terminal and its original wire. Make sure the ammeter (-) lead is connected to the original wire disconnected from the generator.

Secure each connection firmly and tightly, as high current will flow through the terminals. Do not use alligator clips when connecting to the electrical circuit.

6. Connect a voltmeter (0–20 V scale) between the generator "B" terminal and ground. Connect the voltmeter (+) lead to the generator "B" terminal, then the voltmeter (-) lead to a suitable ground (body).

7. Connect a test tachometer according to the manufacturer's instructions. Connect the lead to the battery (-) terminal.

8. Leave the hood open.

INSPECTION PROCEDURE

1. Make sure the voltmeter shows the battery voltage. If the voltmeter shows 0 V, either the circuit between the generator "B" terminal and the battery (-) terminal is open, the fusible link is blown, or there is a poor ground connection.

2. Start the engine and turn on the headlights.

3. Turn on the high beams and set the blower motor switch to "HIGH", then quickly increase engine speed to 2500 rpm and read the maximum generator output current (shown on the ammeter).

After the engine starts, the charging current drops quickly. Perform the test as quickly as possible to record the maximum generator output current.

RESULT ANALYSIS 1. The ammeter reading should be above the minimum allowable value. If the ammeter reading is below the minimum allowable value and the generator "B" terminal circuit is good, remove the generator from the vehicle and test it on a bench.

Minimum allowable value: generator 75 A: minimum 52.5 A; generator 90 A: minimum 63.0 A

1 The generator rated output is stamped on the plate attached to the generator housing.

2. Output current varies depending on the generator load and generator housing temperature. Therefore, the rated output may not be reached. In such cases, to increase the electrical load (to discharge the battery), turn on the high beams for a short time or connect the exterior lighting system of another vehicle.

The rated output current may also not be obtained if the generator housing is overheated or the ambient air temperature is too high. In such cases, let the generator cool down and repeat the test.

2. After completing the generator output current test, gradually reduce engine speed to idle, then turn off the ignition.

3. Disconnect the wire from the negative (-) battery terminal.

4. Remove the ammeter, voltmeter and test tachometer.

5. Connect the original wire to the generator "B" terminal.

6. Connect the wire to the negative (-) battery terminal.