Alternator Diagnostic Procedures - Shibaura N843L Workshop Manual

Construction
The principal components of the IC alternator are the stator,
the rotor, the rectifier assembly, the IC voltage regulator, the
front bracket, the rear bracket and the pulley.
The rectifier assembly consists of two heatsinks, one
positive and one negative, and diode trio.
The diode trio is used as field supply diode and is
connected to the field coil and the terminal L on the
alternator.
The built-in IC regulator is a solid-state unit so that it can
only be serviced as an assembly.

Alternator diagnostic procedures

Checking the regulator adjusting voltage.
1. In equipment without an ammeter, connect a
ammeter (50A capacity) at the position shown in
page 5-5, Fig. 5-12. In equipment with an ammeter,
make use of the ammeter on the equipment.
2. Connect a voltmeter between the terminal B of the
alternator and the ground. The reading on the
voltmeter should indicate the battery voltage. If the
voltmeter reading is zero, the wiring between the
terminal B and the battery is faulty.
3. With the test ammeter terminals short-circuited, start
the engine.
Caution: If the test ammeter is connected at the
position shown in
make sure that no starting current is
applied to the ammeter when the engine is
started.
4. Remove the short circuit across the test ammeter
terminals and
immediately to approx. 2000 rpm. Note the ammeter
reading.
5. If the ammeter reading is 5A or less, note the
voltmeter reading without changing the engine
speed (approx. 2000 rpm). The reading is the
adjusting voltage.
6. If the ammeter reading is more than 5A, continue to
charge the battery until the reading falls to less than
5A or replace the battery with one that is fully
charged.
7. An alternative method is to limit the charging current
by connecting a 1/4 ohm (25W) resistor in series with the battery.
Checking output
If the results of the of the regulator adjusting voltage are within specification, check alternator output:
1. Turn ignition switch to off position, disconnect the terminal B of the alternator and connect an ammeter (50A
capacity) at the position shown in page 5-5, Fig. 5-12.
2. Connect the voltmeter between the terminal B of the alternator and the ground. Confirm that the voltmeter
indicates the battery voltage.
3. Turn ignition switch to on position.
4. Start the engine and turn on all the lamps. Immediately accelerate the engine to 2000 rpm or more and note the
maximum value indicated on the ammeter.
5. If this value is more than 70% of the nominal output (refer to page 7-1, Section 7:Servicing Specifications), the
alternator can be considered as working satisfactorily.
Note: To make the above judgment more accurate, remove the alternator from the engine and check it on a
test bench.
109823_2/09
page 5-5, Fig. 5-12,
increase the engine
IC voltage regulator
Bush
Rectifier
B
V
Alternator
speed
5-5
Rotor
Stator
Front bracket
Rear bracket
Fig. 5-11
Key switch
L
R
Fig. 5-12
Pulley
A
Battery