Mitsubishi Grandis. Manual — part 646
CHARGING SYSTEM
ENGINE ELECTRICAL
16-8
REGULATED VOLTAGE TEST
M1161001100473
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.)
• Drive belt tension
(Refer to
, GROUP 11A
− On-Vehicle
Service.)
• 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
− 150 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 the MUT-III (to show the engine speed).
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.
AK304844 AB
Battery
Ignition
switch-IG
Engine-ECU
<M/T> or
Engine-A/T-
ECU <A/T>
Ammeter (clamp-type)
Load
Black
MB991519
Voltmeter (digital-type)
Red
Yellow
Blue
Alternator
B
FR
L
S
G
Charging
warning lamp
Combination meter
+
-
+
-
CHARGING SYSTEM
ENGINE ELECTRICAL
16-9
13.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.
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 MUT-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:
WAVEFORM CHECK USING AN OSCILLOSCOPE
M1161001200179
MEASUREMENT METHOD
Connect the oscilloscope special patterns pick-up to
the alternator "B" terminal.
STANDARD WAVEFORM
Observation Conditions
Inspection terminal
Voltage regulator ambient
temperature
°C
Voltage V
Terminal "S"
−20
14.2
− 15.4
20
13.9
− 14.9
60
13.4
− 14.6
80
13.1
− 14.5
AK100002
Alternator
"B" terminal
CH1
AC
Function
Special pattern
Pattern height
Variable
Variable knob
Adjust while viewing the waveform.
Pattern selector
Raster
Engine speed
Curb idle speed
CHARGING SYSTEM
ENGINE ELECTRICAL
16-10
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.
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.
AKX00189
0.4
(V)
0.2
0
–0.2
–0.4
Voltage at
alternator
"B" terminal
Time
AG
AKX00190
CHARGING SYSTEM
ENGINE ELECTRICAL
16-11
Abnormal waveform
Problem cause
Example 1
Open diode
Example 2
Short in diode
Example 3
Broken wire in
stator coil
Example 4
Short in stator
coil
AKX00191
AKX00192
AKX00193
AKX00194
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