CHARGING SYSTEM
TSB Revision
ENGINE ELECTRICAL
16-9
• MB991910: M.U.T.-III Main Harness A
This test determines whether the generator outputs
normal current. For best results, use a charging sys-
tem tester. If not available, follow the steps below.
WARNING
Battery posts, terminals and related acces-
sories contain lead and lead compounds.
WASH HANDS AFTER HANDLING.
1. Before the test, always be sure to check the
following.
• Generator installation
• Battery (Refer to GROUP 54A, Chassis Electrical
− Battery − On-vehicle Service − Battery Test
P.54A-9
.)
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 GROUP
00, General
− Maintenance Service − Drive Belts
(For Generator, Power Steering Pump and Air
Conditioning) (Check)
P.00-66
.)
• 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 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, turning on the air conditioner switch 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
Generator Specifications.
NOTE: The current output value will depend on
the electrical load and the temperature of the gen-
erator body.
NOTE: If the electrical load is small while testing,
the specified level of current may not be output
even though the generator is normal. In such
cases, increase the electrical load by leaving the
headlights turned on for some time to discharge
the battery or by using the lighting system in
another vehicle, and then test again.
NOTE: The specified level of current also may not
be output if the temperature of the generator body
or the ambient temperature is too high. In such
cases, cool the generator and then test again.
12.The reading on the ammeter should be above the
limit value. If the reading is below the limit value
and the generator output wire is normal, remove
the generator from the engine and check the
generator.
13.Run the engine at idle speed after the test.
14.Turn the ignition switch to the "LOCK" (OFF)
position.
15.Disconnect the engine tachometer or scan tool
MB991958.
16.Disconnect the negative battery cable.
17.Disconnect the ammeter and voltmeter.
18.Connect the negative battery cable.