Page 69 of 788
CHARGING SYSTEM
ENGINE ELECTRICAL16-5
OUTPUT CURRENT TESTM1161001000368
This test determines whether the alternator output
current is normal.
1. Before the test, always be sure to check the
following.
•Alternator installation
•Battery (Refer to GROUP 54A − Battery −
On-vehicle Service P.54A-5).
NOTE: The battery should be slightly discharged.
The load needed by a fully-charged battery is
insufficient for an accurate test.
•Drive belt tension
(Refer to GROUP 11A − On-vehicle Service <4G1>
P.11A-7 or GROUP 11C − On-vehicle Service
<4G6> P.11C-7.)
•Fusible link
•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.CAUTION
Never use clips but tighten bolts and nuts to
connect the line. Otherwise loose connections
(e.g. 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 − 120 A to the alternator "B" terminal
output wire.
NOTE: The way of disconnecting the alternator
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 alternator "B" terminal and the earth
[Connect the (+) lead of the voltmeter to the "B"
terminal, and then connect the (-) lead of the
voltmeter to the earth].
6. Connect the negative battery cable.
AK203362
Alternator Ammeter
(clamp-type)
Voltmeter
Battery Inition switch
Engine-ECU
or
Engine-A/T-ECU
Load
B
FR
L
S
G +
AH
–
Charging indicator
Brake warning light
Page 70 of 788
CHARGING SYSTEM
ENGINE ELECTRICAL16-6
7. Connect a tachometer or the MUT-II/III (Refer to
GROUP 11A − On-vehicle Service − Idle speed
check <4G1> P.11A-11 or GROUP 11C −
On-vehicle Service − Idle speed check <4G6>
P.11C-11).
8. Leave the hood open.
9. 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 "B" terminal and the battery (+)
terminal.
10.Turn the light switch on to turn on headlamps and
then start the engine.
11.Immediately after setting the headlamps to high
beam and turning the heater blower switch to the
high revolution position, increase the engine
speed to 2,500 r/min and read the maximum
current output value displayed on the ammeter.
Limit: 70 % of normal current outputNOTE: .
•For the nominal current output, refer to the
Alternator Specifications.
•Because the current from the battery will soon
drop after the engine is started, the above step
should be carried out as quickly as possible in
order to obtain the maximum current output
value.
•The current output value will depend on the
electrical load and the temperature of the
alternator body.
•If the electrical load is small while testing, the
specified level of current may not be output
even though the alternator is normal. In such
cases, increase the electrical load by leaving
the headlamps turned on for some time to
discharge the battery or by using the lighting
system in another vehicle, and then test again.
•The specified level of current also may not be
output if the temperature of the alternator body
or the ambient temperature is too high. In such
cases, cool the alternator 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 alternator output wire is normal, remove
the alternator from the engine and check the
alternator.
13.Run the engine at idle after the test.
14.Turn the ignition switch to the "LOCK" (OFF)
position.
15.Remove the tachometer or the MUT-II/III.
16.Disconnect the negative battery cable.
17.Disconnect the ammeter and voltmeter.
18.Connect the negative battery cable.
Page 71 of 788
CHARGING SYSTEM
ENGINE ELECTRICAL16-7
REGULATED VOLTAGE TESTM1161001100354
This test determines whether the voltage regulator
correctly controlling the alternator output voltage.
1. Always be sure to check the following before the
test.
•Alternator installation
•Check that the battery installed in the vehicle is
fully charged.
(Refer to GROUP 54A − Battery − On-vehicle
Service − Charging P.54A-4).
•Drive belt tension
(Refer to GROUP 11A − On-vehicle Service <4G1>
P.11A-7 or GROUP 11C − On-vehicle Service
<4G6> P.11C-7.)
•Fusible link
•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 "S"
terminal, and then connect the (-) lead of the
voltmeter to a secure earth or to the battery (-)
terminal].
5. Connect a clamp-type DC test ammeter with a
range of 0 − 120 A to the alternator "B" terminal
output wire.NOTE: The way of disconnecting the alternator
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.
6. Reconnect the negative battery cable.
7. Connect a tachometer or the MUT-II/III (Refer to
GROUP 11A − On-vehicle Service − Idle speed
check <4G1> P.11A-11 or GROUP 11C −
On-vehicle Service − Idle speed check <4G6>
P.11C-11).
8. 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 "S" terminal and the battery (+)
terminal.
9. Turn all lamps and accessories off.
10.Start the engine.
11.Increase the engine speed to 2,500 r/min.
12.Read the value displayed on the voltmeter when
the alternator output current alternator becomes
10 A or less.
13.If the voltage reading conforms to the value in the
voltage regulation, then the voltage regulator is
operating normally.
AK300727AB
BatteryIgnition switch
Engine-ECU
Engine-A/T-ECU Ammeter (clamp-type)Load
Black MB991519
Voltmeter (digital-type) Red
YellowBlueAlternator B
FR
L
S
G
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CHARGING SYSTEM
ENGINE ELECTRICAL16-8
If the voltage is not within the standard value,
there is a malfunction of the voltage regulator or of
the alternator.
14.After the test, lower the engine speed to the idle
speed.
15.Turn the ignition switch to the "LOCK" (OFF)
position.
16.Remove the tachometer or the MUT-II/III.17.Disconnect the negative battery cable.
18.Disconnect the ammeter and voltmeter.
19.Connect the alternator output wire to the
alternator "B" terminal.
20.Remove the special tool, and return the connector
to the original condition.
21.Connect the negative battery cable.
Voltage Regulation Table
Standard value:
Inspection terminal Voltage regulator ambient
temperature °CVoltage V
Terminal "S"
−2014.2 − 15.4
20 13.9 − 14.9
60 13.4 − 14.6
80 13.1 − 14.5
Page 73 of 788
CHARGING SYSTEM
ENGINE ELECTRICAL16-9
WAVEFORM CHECK USING AN OSCILLOSCOPEM1161001200124
MEASUREMENT METHODConnect the oscilloscope special patterns pick-up to
the alternator "B" terminal.
STANDARD WAVEFORM
Observation Conditions
NOTE:
The voltage waveform of the alternator "B" terminal
can undulate as shown in the illustration. This
waveform is produced when the regulator operates
according to fluctuations in the alternator load (current), and is normal for the alternator. In addition,
when the voltage waveform reaches an excessively
high value (approximately 2 V or higher at idle), it
often indicates an open circuit due to a brown fuse
between alternator "B" terminal and battery, but not a
defective alternator.
AK100002
Alternator
"B" terminalCH1
AC
Function Special pattern
Pattern height Variable
Variable knob Adjust while viewing the waveform.
Pattern selector Raster
Engine speed Curb idle speed
AKX00189
0.4 (V)
0.2
0
–0.2
–0.4 Voltage at
alternator
"B" terminal
Time
AG
AKX00190
Page 74 of 788
CHARGING SYSTEM
ENGINE ELECTRICAL16-10
EXAMPLE OF ABNORMAL WAVEFORMS
NOTE: .
1. The size of the waveform patterns differs largely, depending on the adjustment of the variable knob on the
oscilloscope.
2. Identification of abnormal waveforms is easier when there is a large output current (regulator is not
operating). (Waveforms can be observed when the headlamps are illuminated.)
3. Check the conditions of the charging warning lamp (illuminated/not illuminated). Also, check the charging
system totally.
Abnormal waveform Problem cause
Example 1 Open diode
Example 2 Short in diode
AKX00191
AKX00192
Page 75 of 788
CHARGING SYSTEM
ENGINE ELECTRICAL16-11
Example 3 Broken wire in
stator coil
Example 4 Short in stator
coil
Example 5
At this time, the charging warning lamp is illuminated.Open
supplementary
diode Abnormal waveform Problem cause
AKX00193
AKX00194
AKX00195
Page 76 of 788
