Jeep 1997 Grand Cherokee Service Manual page 333

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GENERAL INFORMATION
OVERVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
DESCRIPTION AND OPERATION
BATTERY TEMPERATURE SENSOR . . . . . . . . . 2
CHARGING SYSTEM OPERATION
ELECTRONIC VOLTAGE REGULATOR
GENERATOR . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
DIAGNOSIS AND TESTING
BATTERY TEMPERATURE SENSOR . . . . . . . . . 5
CHARGING SYSTEM RESISTANCE TESTS . . . . 3
GENERAL INFORMATION
OVERVIEW
The battery, starting, and charging systems oper-
ate with one another, and must be tested as a com-
plete system. In order for the vehicle to start and
charge properly, all of the components involved in
these systems must perform within specifications.
Group 8A covers the battery, Group 8B covers the
starting system, and Group 8C covers the charging
system. Refer to Group 8W - Wiring Diagrams for
complete circuit descriptions and diagrams. We have
separated these systems to make it easier to locate
the information you are seeking within this Service
Manual. However, when attempting to diagnose any
of these systems, it is important that you keep their
interdependency in mind.
The diagnostic procedures used in these groups
include the most basic conventional diagnostic meth-
ods to the more sophisticated On-Board Diagnostics
(OBD) built into the Powertrain Control Module
(PCM). Use of a induction milliampere ammeter, volt/
ohmmeter, battery charger, carbon pile rheostat (load
tester), and 12-volt test lamp may be required.
All OBD-sensed systems are monitored by the
PCM. Each monitored circuit is assigned a Diagnos-
tic Trouble Code (DTC). The PCM will store a DTC in
electronic memory for any failure it detects. See the
On-Board Diagnostics Test in Group 8C - Charging
System for more information.
DESCRIPTION AND OPERATION
CHARGING SYSTEM OPERATION
The charging system consists of:
• Generator
CHARGING SYSTEM
CONTENTS
page
. . . . . . . . . . 1 REMOVAL AND INSTALLATION
. . . . . . . 2
SPECIFICATIONS
within the Powertrain Control Module (PCM)
tem for information)
tion)
and Gauges for information)
8W, Wiring for information)
ignition switch. When the ignition switch is turned to
the ON position, battery voltage from the powertrain
control module (PCM) is supplied to the generator
rotor to produce a magnetic field. This is done
through one of the two field terminals at the rear of
generator. On models of previous years, battery
voltage to this field terminal was supplied
directly from the ASD relay.
ator is controlled by the EVR (field control) circuitry
contained within the PCM. This circuitry is con-
nected in series with the second rotor field terminal
and ground.
tery tray housing, is used to sense battery tempera-
ture. This temperature data, along with data from
monitored line voltage, is used by the PCM to vary
the battery charging rate. This is done by cycling the
ground path to control the strength of the rotor mag-
netic field. The PCM then compensates and regulates
generator current output accordingly.
tics (OBD). All OBD-sensed systems, including the
EVR (field control) circuitry, are monitored by the
CHARGING SYSTEM
CHARGING SYSTEM . . . . . . . . . . . . . . . . . . . . . 2
CURRENT OUTPUT TEST . . . . . . . . . . . . . . . . . 3
ON-BOARD DIAGNOSTIC TEST FOR
CHARGING SYSTEM . . . . . . . . . . . . . . . . . . . 5
BATTERY TEMPERATURE SENSOR . . . . . . . . . 7
GENERATOR . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
GENERATOR RATINGS . . . . . . . . . . . . . . . . . . . 7
TORQUE SPECIFICATIONS . . . . . . . . . . . . . . . . 7
• Electronic Voltage Regulator (EVR) circuitry
• Ignition switch (refer to Group 8D, Ignition Sys-
• Battery (refer to Group 8A, Battery for informa-
• Battery temperature sensor
• Generator Lamp (if equipped)
• Check Gauges Lamp (if equipped)
• Voltmeter (refer to Group 8E, Instrument Panel
• Wiring harness and connections (refer to Group
The charging system is turned on and off with the
The amount of DC current produced by the gener-
A battery temperature sensor, located in the bat-
All vehicles are equipped with On-Board Diagnos-
8C - 1
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