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CHARGING SYSTEM
ENGINE ELECTRICAL16-2
CHARGING SYSTEM
GENERAL INFORMATIONM1161000100522
The charging system uses the alternator output to
keep the battery charged at a constant level under
various electrical loads.
OPERATION
Rotation of the excited field coil generates AC
voltage in the stator.
This alternating current is rectified through diodes to
DC voltage having a waveform shown in the
illustration.The average output voltage fluctuates slightly with
the alternator load condition.
When the ignition switch is turned on, current flows in
the field coil and initial excitation of the field coil
occurs.
When the stator coil begins to generate power after
the engine is started, the field coil is excited by the
output current of the stator coil.
The alternator output voltage rises as the field
current increases and it falls as the field current
decreases. When the battery voltage (alternator "S"
terminal voltage) reaches a regulated voltage of
approximately 14.4 V, the field current is cut off.
When the battery voltage drops below the regulated
voltage, the voltage regulator regulates the output
voltage to a constant level by controlling the field
current.
In addition, when the field current is constant, the
alternator output voltage rises as the engine speed
increases.
SYSTEM DIAGRAM
ALTERNATOR SPECIFICATIONS
AKX00183
Voltage
Time
Approximately
14.4 V
AC
AK400308
Alternator
B
Stator coil
Engine-ECU
or
Engine-A/T-ECU
G
S
L
FR <4G1>
Voltage regulatorCharge warning lightIgnition switch
Battery Field coil
+
–
AB
Item 4G1 4G6
Type Battery voltage sensing
Rated output V/A 12/80 12/110
Voltage regulator Electronic built-in type
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CHARGING SYSTEM
ENGINE ELECTRICAL16-3
SERVICE SPECIFICATIONSM1161000300258
SPECIAL TOOLM1161000600163
ON-VEHICLE SERVICE
ALTERNATOR OUTPUT LINE VOLTAGE DROP TESTM1161000900346
This test determines whether the wiring from the
alternator "B" terminal to the battery (+) terminal
(including the fusible line) is in a good condition or
not.
1. Always be sure to check the following before the
test.
•Alternator installation•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 Item Standard value Limit
Alternator output line voltage drop (at 30 A) V
−maximum 0.3
Regulated voltage ambient
temperature at voltage regulator V−20°C14.2 − 15.4
−
20°C 13.9 − 14.9
−
60°C 13.4 − 14.6
−
80°C 13.1 − 14.5
−
Output current
−70 % of normal output current
Tool Number Name Use
MB991519 Alternator test harness Checking the alternator
("S" terminal voltage)
AK203361AD
AlternatorAmmeter (clamp-type)
Voltmeter (digital-type)
"B" terminalBattery
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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
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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 ELECTRICAL16-9
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
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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
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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
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