Battery - Dodge ram truck 3500 1996 Service Manual

oh - 1 CHARGING SYSTEM
B R
D E S C R I P T I O N AND OPERATION (Continued)
All vehicles are equipped with On-Board Diagnos­
tics (OBD). A l l OBD-sensed systems, including the
EVR (field control) circuitry, 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 i t 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. I t is serviced only as a
complete assembly. I f 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, i t 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 (snapped into) the battery tray (Fig. 1).
On models equipped with a diesel engine (dual bat­
teries), only one sensor is used. Location is under
battery on drivers side of vehicle.
VOLTAGE REGULATOR
The voltage regulator is not a separate component.
It is actually a voltage regulating circuit located
within the PCM. This EVR is not serviced separately.
BATTERY
Fig. 1 Battery Temperature Sensor Location
I f 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 i n
series with the generators second rotor field terminal
and its ground.
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). I t then compensates and
regulates generator current output accordingly. Also
see Charging System Operation for additional infor­
mation.
D I A G N O S I S A N D T E S T I N G
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 i n ON)
should register.