Jeep 1997 Grand Cherokee Service Manual page 706

8W - 20 - 6
DESCRIPTION AND OPERATION
CHARGING SYSTEM
The charging system is an integral part of the bat-
tery and starting systems. Because all these systems
work in conjunction, diagnose and test them together.
Circuit A11 connects to the generator output termi-
nal and the Power Distribution Center (PDC). Circuit
A0 connects the battery to the PDC. Circuit Z0 pro-
vides ground for the generator.
When the ignition switch is in either the START or
RUN positions, it connects circuit A1 from fuse 8 in
the PDC to circuit A21. Circuit A21 powers circuit
F99 through fuse 18 in the PDC. Circuit F99 splices
to supply current to the coil side of the Automatic
Shut Down (ASD) relay. The Powertrain Control
Module (PCM) provides ground for the relay on cir-
cuit K900. Circuit K900 connects to cavity C3 of the
PCM.
When the PCM grounds the ASD relay, contacts
inside the relay close and connect circuit F5 from the
fuse 20 in the PDC to circuit A142. Circuit A142
splices to supply system voltage to cavity C12 of the
PCM. Circuit K72 from Cavity C25 of the PCM sup-
plies current to the generator field terminal..
The PCM has an internal voltage regulator that
controls generator output. The PCM controls the gen-
erator field on circuit K20. Circuit K20 connects to
PCM cavity B10.
When the engine operates and there is current in
the generator field, the generator produces a B+ volt-
age. The generator supplies B+ voltage to the battery
through the A11 and A0 circuits.
8W - 20 CHARGING SYSTEM
8W-20 CHARGING SYSTEM
HELPFUL INFORMATION
• Circuit A21 passes through the junction block
before reaching fuse 18 in the PDC.
• The ASD relay supplies battery voltage for the
fuel injectors, ignition coil, and the heated oxygen
sensors.
CHARGING SYSTEM (DIESEL)
The charging system is an integral part of the bat-
tery and starting systems. Because all these systems
work in conjunction, diagnose and test them together.
Circuit A11 connects to the generator output termi-
nal and the Power Distribution Center (PDC). Circuit
A0 connects the battery to the PDC. The generator is
case grounded.
Power for the field terminal in the generator is
supplied on circuit A142. This circuit is HOT when
the contacts in the Automatic Shut Down (ASD) relay
are CLOSED.
The PCM has an internal voltage regulator that
controls generator output. The PCM controls the gen-
erator field on circuit K20.
When the engine operates and there is current in
the generator field, the generator produces a B+ volt-
age. The generator supplies B+ voltage to the battery
through the A11 and A0 circuits.
HELPFUL INFORMATION
• Check the 175 amp fuse in the PDC
• Check the 25 amp fuse located in cavity F20 of
the PDC
ZG