Subaru LEGACY 2002 Quick Reference Index page 179

2. Generator
The generator has a built-in regulator which provides diagnostic functions in addition to a voltage
regulating function as follows:
1) Voltage regulation
The on-off operation of transistor Tr
a constant level of output voltage.
2) Diagnosis warning
When any of the following problems occur, the charge lamp illuminates.
a. No voltage generation
Brush wear exceeds specified wear limits, field coil circuit is broken, etc.
b. Excessive output
Output voltage is greater than 16 volts (approx.)
c. Terminal B disconnection
Harness is disconnected from alternator terminal B.
d. Terminal S disconnection
Harness is disconnected from alternator terminal S. In this case, voltage is slightly greater than
specified regulated voltage; however, voltage regulation is still controlled and the battery is pre-
vented from becoming overcharged.
Plus diode (3 pcs.)
Additional diode (2 pcs.)
Stator coil
Field coil
GENERATOR
connects and disconnects the field current circuit, providing
1
Trio diode (3 pcs.)
T
F
Tr1
Constant
voltage
circuit
E
IC regulator
Minus diode (3 pcs.)
SC-3
B
B
Energizing
circuit
Tr3
S S
L L
Tr2
Diagnostic
and warning
circuit
: Alternator terminal
: Regulator terminal
Starting/Charging
IG switch
Charge
light
B2H3981A