Mitsubishi Space Star. Manual — part 96

ENGINE ELECTRICAL –

Charging System

16-3

ON-VEHICLE SERVICE <Diesel-powered vehicle>

ALTERNATOR OUTPUT LINE VOLTAGE DROP TEST

Alternator

Terminal B

Voltmeter

+

+

–

–

Ammeter

Battery

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

Alternator drive belt tension (Refer to
GROUP 11C – On-vehicle Service.)

Fusible link

Abnormal noise from the alternator while
the engine is running

(2) Turn the ignition switch off.
(3) Disconnect the negative battery cable.
(4) Disconnect the alternator output wire from the

alternator “B” terminal and connect a DC test
ammeter with a range of 0 – 100 A in series
between the “B” terminal and the disconnected

output wire. (Connect the (+) lead of the
ammeter to the “B” terminal, and then connect
the (–) lead of the ammeter to the disconnected
output wire.)

NOTE
An inductive-type ammeter which enables
measurements to be taken without disconnect-
ing the alternator output wire should be
recommended. Using this equipment will lessen
the possibility of a voltage drop caused by a
loose “B” terminal connection.

(5) Connect a digital-type voltmeter between the

alternator “B” terminal and the battery (+)
terminal. (Connect the (+) lead of the voltmeter
to the “B” terminal and the connect the (–) lead
of the voltmeter to the battery (+) cable.)

ENGINE ELECTRICAL –

Charging System

16-4

(6) Connect a tachometer.
(7) Reconnect the negative battery cable.
(8) Leave the hood open.
(9) Start the engine.
(10)With the engine running at 2,500 r/min, turn

the headlamps and other lamps on and off to
adjust the alternator load so that the value
displayed on the ammeter is slightly above 30
A.
Adjust the engine speed by gradually
decreasing it until the value displayed on the
ammeter is 30 A. Take a reading of the value
displayed on the voltmeter at this time.

Limit: max. 0.3 V

NOTE
When the alternator output is high and the value
displayed on the ammeter does not decrease
until 30 A, set the value to 40 A. Read the
value displayed on the voltmeter at this time.

(11) If the value displayed on the voltmeter is above

the limit value, there is probably a malfunction
in the alternator output wire, so check the wiring
between the alternator “B” terminal and the
battery (+) terminal (including fusible link).
If a terminal is not sufficiently tight or if the
harness has become discolored due to
overheating, repair and then test again.

(12)After the test, run the engine at idle.
(13)Turn all lamps and the ignition at idle.
(14)Disconnect the negative batter cable.
(15)Disconnect the ammeter, voltmeter and

tachometer.

(16)Connect the alternator output wire to the

alternator “B” terminal.

(17)Connect the negative battery cable.

OUTPUT CURRENT TEST

80 A

30 A

Battery

Charging warning lamp

Ignition switch

Voltmeter

Ammeter

Load

L

B

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 54 – Battery.)

NOTE
The used battery should be slightly
discharged. The load needed by a
fully-charged battery is insufficient for an
accurate test.

Alternator drive belt tension (Refer to
GROUP 11C – On-vehicle Service.)

Fusible link

Abnormal noise from the alternator while
the engine is running.

ENGINE ELECTRICAL –

Charging System

16-5

(2) Turn the ignition switch off.
(3) Disconnect the negative battery cable.
(4) Disconnect the alternator output wire from the

alternator “B” terminal. Connect a DC test
ammeter with a range of 0 – 100 A in series
between the “B” terminal and the disconnected
output wire. (Connect the (+) lead of the
ammeter to the “B” terminal. Connect the (–)
lead of the ammeter to the disconnected output
wire.)

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.

NOTE
An inductive-type ammeter which enables
measurements to be taken without disconnect-
ing the alternator output wire should be
recommended.

(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 a tachometer.
(7) Connect the negative battery cable.
(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 output

NOTE

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 off.
(15)Disconnect the negative battery cable.
(16)Disconnect the ammeter, voltmeter and

tachometer.

(17)Connect the alternator output wire to the

alternator “B” terminal.

(18)Connect the negative battery cable.

ENGINE ELECTRICAL –

Charging System

16-6

REGULATED VOLTAGE TEST

Battery

Ignition
switch (IG1)

Voltmeter

Alternator

Ammeter

L

B

Load

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.

Alternator installation

Check that the battery installed in the vehicle
is fully charged. (Refer to GROUP 54 –
Battery.)

Alternator drive belt tension (Refer to
GROUP 11C – On-vehicle Service.)

Fusible link

Abnormal noise from the alternator while
the engine is running

(2) Turn the ignition switch to the OFF position.
(3) Disconnect the negative battery cable.
(4) Connect a digital-type voltmeter between the

alternator “L” terminal and the earth. (Connect
the (+) lead of the voltmeter to the “L” 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 “B” terminal.

(6) Connect a DC test ammeter with a range of

0 – 100 A in series between the “B” terminal
and the disconnected output wire. (Connect the
(+) lead of the ammeter to the “B” terminal.
Connect the (–) lead of the ammeter to the
disconnected output wire.)

(7) Connect a tachometer.
(8) Reconnect the negative battery cable.
(9) Turn the ignition switch to the ON position and

check that the reading on the voltmeter is 2
– 5 V.

NOTE
If the voltage is 0 V, the cause is probably an
open circuit in the wire or fusible link between
the alternator “L” 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.