Rotation of the excited field coil generates AC volt-
age in the stator.
This alternating current is rectified through diodes to
DC voltage having a waveform shown in the illustra-
tion.

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 cur-
rent 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 cur-
rent.
In addition, when the field current is constant, the
alternator output voltage rises as the engine speed
increases.

SYSTEM DIAGRAM

AK304222

Alternator

Stator coil

Engine-ECU

Voltage
regulator

Charge
warning lamp

Ignition switch

Battery

Field coil

–

CHARGING SYSTEM

ENGINE ELECTRICAL

16-3

ALTERNATOR SPECIFICATIONS

Item

Specifications

Type

Battery voltage sensing

Rated output V/A

12/90

Voltage regulator

Electronic built-in type

SERVICE SPECIFICATIONS

M1161000300407

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°C

14.2

− 15.4

−

°C

13.9

− 14.9

−

°C

13.4

− 14.6

−

°C

13.1

− 14.5

−

Output current

−

70 % of normal output current

CHARGING SYSTEM

ENGINE ELECTRICAL

16-4

SPECIAL TOOL

M1161000600356

Tool

Number

Name

Use

B991502

MB991502

M.U.T.-II sub assembly

• Checking the idle speed

MB991910

MB991826

MB991955

MB991911

MB991824

MB991827

MB991825

DO NOT USE

MB991955
A:
MB991824
B:
MB991827
C:
MB991910
D:
MB991911
E:
MB991825
F:
MB991826

M.U.T.-III sub assembly

• A: Vehicle

communication
interface (V.C.I.)

• B: M.U.T.-III USB

cable

• C: M.U.T.-III main

harness A (Vehicles
with CAN
communication
system)

• D: M.U.T.-III main

harness B (Vehicles
without CAN
communication
system)

• E: M.U.T.-III

measurement adapter

• F: M.U.T.-III trigger

harness

• Checking the idle speed

M.U.T.-III main harness B
(MB991911) should be used.
M.U.T.-III main harness A should
not be used for this vehicle.

MB991519

Alternator test harness

Checking the alternator
("S" terminal voltage)

CAUTION

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