Description And Operation; Battery Temperature Sensor; Charging System Operation; Generator - Jeep 1996 Grand Cherokee Service Manual

8C - 2 CHARGING SYSTEM
DESCRIPTION AND OPERATION (Continued)
electronic memory for any failure it detects. See On-
Board Diagnostic System Test in this group for more
information.

GENERATOR

The generator is belt-driven by the engine using a
serpentine type drive belt. It is serviced only as a
complete assembly. If the generator fails for any rea-
son, the entire assembly must be replaced.
As the energized rotor begins to rotate within the
generator, the spinning magnetic field induces a cur-
rent into the windings of the stator coil. Once the
generator begins producing sufficient current, it also
provides the current needed to energize the rotor.
The Y type stator winding connections deliver the
induced AC current to 3 positive and 3 negative
diodes for rectification. From the diodes, rectified DC
current is delivered to the vehicle electrical system
through the generator battery and ground terminals.
Although the generators appear the same exter-
nally, different generators with different output rat-
ings are used on this vehicle. This will depend upon
engine size and optional equipment. Be certain that
the replacement generator has the same output rat-
ing as the original unit. See Generator Ratings in the
Specifications section at the back of this group for
amperage ratings.
Noise emitting from the generator may be caused
by: worn, loose or defective bearings; a loose or defec-
tive drive pulley; incorrect, worn, damaged or misad-
justed fan drive belt; loose mounting bolts; a
misaligned drive pulley or a defective stator or diode.

BATTERY TEMPERATURE SENSOR

The battery temperature sensor is used to deter-
mine the battery temperature and control battery
charging rate. This temperature data, along with
data from monitored line voltage, is used by the PCM
to vary the battery charging rate. System voltage will
be higher at colder temperatures and is gradually
reduced at warmer temperatures.
The sensor is located under the vehicle battery,
and is attached to the battery tray (Fig. 1).

VOLTAGE REGULATOR

The Electronic Voltage Regulator (EVR) is not a
separate component. It is actually a voltage regulat-
ing circuit located within the Powertrain Control
Module (PCM). The EVR is not serviced separately. If
replacement is necessary, the PCM must be replaced.
Operation: The amount of DC current produced
by the generator is controlled by EVR circuitry con-
tained within the PCM. This circuitry is connected in
series with the generators second rotor field terminal
and its ground.
Fig. 1 Battery Temperature Sensor
Voltage is regulated by cycling the ground path to
control the strength of the rotor magnetic field. The
EVR circuitry monitors system line voltage and bat-
tery temperature (refer to Battery Temperature Sen-
sor for more information). It then compensates and
regulates generator current output accordingly. Also
see Charging System Operation for additional infor-
mation.

DIAGNOSIS AND TESTING

CHARGING SYSTEM
When the ignition switch is turned to the ON posi-
tion, battery potential will register on the voltmeter.
During engine cranking a lower voltage will appear
on the meter. With the engine running, a voltage
reading higher than the first reading (ignition in ON)
should register.
The following procedures may be used to diagnose
the charging system if:
• the voltmeter does not operate properly
• an undercharged or overcharged battery condi-
tion occurs.
Remember that an undercharged battery is often
caused by:
• accessories being left on with the engine not
running
• a faulty or improperly adjusted switch that
allows a lamp to stay on. See Ignition-Off Draw Test
in Group 8A, Battery for more information.
INSPECTION
(1) Inspect condition of battery cable terminals,
battery posts, connections at engine block, starter
solenoid and relay. They should be clean and tight.
Repair as required.
(2) Inspect all fuses in the fuseblock module and
Power Distribution Center (PDC) for tightness in
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