Output Current 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 generator outputs normal current. For best results, use a charging system tester. If not available, follow the steps below.

1. Before the test, always be sure to check the following.
   • Generator installation
   • Battery (Refer to BATTERY CHECK .)
     NOTE: The battery to be used should be slightly discharged. The load in a fully charged battery will be insufficient and the test may not be able to be carried out correctly.
   • Generator drive belt tension (Refer to DRIVE BELTS (FOR GENERATOR, POWER STEERING PUMP AND AIR CONDITIONING) (CHECK) .)
   • 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.
   WARNING: Never use clips to connect the line. Loose connections (for example, using clips) will lead to a serious accident because of high current.
4. Connect a clamp-type DC test ammeter with a range of 0 - 150 A to the generator "B" terminal output wire.
   NOTE: The way of disconnecting the generator output wire and of connecting the ammeter is possibly not found the problem that the output current is dropping due to the insufficient connection between terminal "B" and the output wire.
5. Connect a voltmeter with a range of 0 - 20 V between the generator "B" terminal and ground. (Connect the positive lead of the voltmeter to the "B" terminal, and then connect the negative lead of the voltmeter to ground.)
6. Connect the negative battery cable.
7. Connect an engine tachometer or scan tool MB991958.
8. Leave the hood open.
9. Check to be sure that the reading on the voltmeter is equal to the battery positive voltage.
   NOTE: If the voltage is 0 V, the cause is probably an open circuit in the wire or fusible link between the generator "B" terminal and the battery positive terminal or malfunctioning voltmeter.
10. After turning on the headlights, start the engine.
    NOTE: Because the current from the battery will soon drop after the engine is started, step 11 should be carried out as quickly as possible in order to obtain the maximum current output value.
11. Immediately after setting the headlights to high beam and turning the heater blower switch to the highest position, increase the engine speed to 2,500 r/min and read the maximum current output value displayed on the ammeter.

    Limit value: 70 % of nominal current output 

    NOTE: For the nominal current output, refer to the SERVICE SPECIFICATIONS  .