16-GENERATOR OUTPUT LINE VOLTAGE DROP TEST

GENERATOR OUTPUT LINE VOLTAGE DROP TEST

Required Special Tool:

MB991958: Scan Tool (M.U.T.-III Sub Assembly)

MB991824: V.C.I.
MB991827: M.U.T.-III USB Cable
MB991910: M.U.T.-III Main Harness A

This test determines whether the wiring from the generator "B" terminal to the positive battery terminal (including the fusible link) is in good condition or not:

warning

Battery posts, terminals and related accessories contain lead and lead compounds. WASH HANDS AFTER HANDLING.

1. Always be sure to check the following before the test.

Generator installation
Generator drive belt tension [Refer to GROUP 00, General - Maintenance Service - Drive Belts (For Generator and Power Steering Oil Pump) (Check Condition) ].
Fusible link
Abnormal noise from the generator while the engine is running.

2. Turn the ignition switch to the "LOCK" (OFF) position.

3. Disconnect the negative battery cable.

4. Set a clamp-type DC test ammeter to the generator "B" terminal output wire.

note	Disconnecting the generator output wire and connecting the ammeter may not thoroughly diagnosis an output current drop problem because of an insufficient connection between terminal "B" and the output wire.

5. Connect a digital-type voltmeter between the generator "B" terminal and the positive battery terminal. (Connect the positive lead of the voltmeter to the "B" terminal, and then connect the negative lead of the voltmeter to the positive battery cable.)

6. Reconnect the negative battery cable.

7. Connect an engine tachometer or scan tool MB991958.

8. Leave the hood open.

9. Start the engine.

10. With the engine running at 2,500 r/min, turn the headlights and other lights on and off to adjust the generator load so that the value displayed on the ammeter is slightly above 30 A.

Adjust the engine speed by gradually decreasing it until the value displayed on the ammeter is 30 A. Take a reading of the valve displayed on the voltmeter at this time.

Limit: maximum 0.3 V

note	When the generator output is high and the value displayed on the ammeter does not decrease until 30 A, set the value to 40 A. Read the value displayed on the voltmeter at this time. When the value range is 40 A, the limit is maximum 0.4 V.

11. If the value displayed on the voltmeter is above the limit value, there is probably a malfunction in the generator output wire. Check the wiring between the generator "B" terminal and the positive battery terminal (including fusible link).

If a terminal is not sufficiently tight or if the harness has become discolored due to overheating, repair and then test again.

12. After the test, run the engine at idle.

13. Turn off all lights and turn the ignition switch to the "LOCK" (OFF) position.

note	Vehicles for Canada, the headlight, taillight, etc. remain lit even when the lighting switch is in "OFF" position.

14. Disconnect the engine tachometer or scan tool MB991958.

15. Disconnect the negative battery cable.

16. Remove the ammeter and voltmeter.

17. Connect the negative battery cable.