GMC 4000 Series Service Manual page 434

No. 7 No.
No. 6
Figure 21 — Regulator with Cover Removed
the 1116378 transistorized regulator, voltage from
"R" terminal on generator is im pressed through
regulator #2 terminal and through field relay wind­
ing causing the relay contacts to close. This con­
nects the regulator #4 terminal directly to battery
through the field relay contacts, causing the indi­
cator lamp to go "OUT." Generator field current
then flows from generator or battery to regulator
#3 terminal, then through the field relay contacts
and transistor TR-1 to the generator field winding.
As generator speed increases, the voltage
reaches the p re-set value and components in the
regulator cause transistor TR-1 to alternately
"turn-off" and "turn-on" the generator field volt­
age. The regulator thus operates to limit the gen­
erator output voltage to the p re-set value.
ANALYZING CHARGING SYSTEM
TROUBLES
NOTE: Procedures for analyzing or checking
charging system trouble are explained previously.
Adapter (J-9782-3) may be used at the regu­
lator to facilitate checking circuits.
If trouble is located in the generator during
the test procedures, refer to the applicable gener­
ator section for corrective procedures.
When analyzing the system , make sure all
connections between the battery, junction block,
and generator are clean and tight, then remove the
wiring harness connector from the regulator and
G M C S E R V I C E M A N U A L
2 No. 1 No. 4
No. 3 No. 5 -5 5 8 9
t
A/C GENERATING SYSTEM
OUTPUT TRANSISTOR
INSULATORS
TRANSISTOR MOUNTING
Figure 2 2 — Heat Sink and Circuit Board Assem bly
connect the adapter between the wiring harness
connector and the regulator.
When the trouble is found, it is not necessary
to make further checks; however, it is often ad­
visable to complete all checks to ensure that no
other troubles exist.
REGULATOR REPLACEMENT
REGULATOR REMOVAL
1. Disconnect the negative cable from battery.
2. Carefully lift up on regulator wiring har­
ness connector with one hand and with the other,
pull harness connector from regulator.
3. Remove regulator mounting screw s, then
remove regulator assembly.
REGULATOR INSTALLATION
IMPORTANT: Make sure one battery cable is
disconnected from battery.
1. Place regulator-to-generator ground wire
on regulator mounting and install regulator at­
taching screw s.
Sec. 6Y
Page 423
M
SCREWS
T-5590