ENGINE ELECTRICAL ± Charging System
16-8
This test determines whether the voltage regulator
is correctly controlling the alternator output voltage.
(1) Always be sure to check the following before
the test.
D Alternator installation
D Check that the battery installed in the vehicle
is fully charged.
D Alternator drive belt tension
D Fusible link
D Abnormal noise from the alternator while
the engine is running
(2) Turn the ignition switch to the LOCK (OFF)
position.
(3) Disconnect the negative battery cable.
(4) Use the special tool (Alternator test harness:
MB991519) to connect a digital voltmeter
between the alternator S terminal and earth.
(Connect the (+) lead of the voltmeter to the
ªSº terminal, and then connect the (−) lead of
the voltmeter to a secure earth or to the battery
(−) terminal.)
(5) Disconnect the alternator output wire from the
alternator ªBº terminal.
(6) Connect a DC test ammeter with a range of
0± 100 A in series between the ªBº terminal
and the disconnected output wire. (Connect the
(+) lead of the ammeter to the ªBº terminal.
Connect the (±) lead of the ammeter to the
disconnected output wire.)
(7) Reconnect the negative battery cable.
(8) Connect a tachometer or the MUT-II.
(9) Turn the ignition switch to the ON position and
check that the reading on the voltmeter is equal
to the battery voltage.
NOTE
If the voltage is 0 V, the cause is probably an
open circuit in the wire or fusible link between
the alternator ªSº terminal and the battery (+)
terminal.
(10)Turn all lamps and accessories off.
(11)Start the engine.
(12)Increase the engine speed to 2,500 r/min.
(13)Read the value displayed on the voltmeter when
the alternator output current alternator becomes
10 A or less.
(14)If the voltage reading conforms to the value
in the voltage regulation, then the voltage
regulator is operating normally.
If the voltage is not within the standard value,
there is a malfunction of the voltage regulator
or of the alternator.
(15)After the test, lower the engine speed to the
idle speed.
(16)Turn the ignition switch to the LOCK (OFF)
position.
(17)Remove the tachometer or the MUT-II.
(18)Disconnect the negative battery cable.
(19)Disconnect the ammeter and voltmeter.
(20)Connect the alternator output wire to the
alternator ªBº terminal.
(21)Remove the special tool, and return the
connector to the original condition.
(22)Connect the negative battery cable.
Voltage Regulation Table
Standard value:
Inspection terminal Voltage regulator ambient temperature _C Voltage V
Terminal ªSº
± 20 14.2± 15.4
20 13.9± 14.9
60 13.4± 14.6
80 13.1± 14.5
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