1998 DODGE RAM 1500 Charging system operation

RADIO NOISE SUPPRESSION
GROUND STRAP
DESCRIPTION
Radio noise suppression devices are factory-in-
stalled standard equipment on this vehicle. Radio
Frequency Interference (RFI) and ElectroMagnetic
Interference (EMI) can be produced by any on-board
or external source of electromagnetic energy. These
electromagnetic energy sources can radiate electro-
magnetic signals through the air, or conduct them
through the vehicle electrical system.
When the audio system converts RFI or EMI to an
audible acoustic wave form, it is referred to as radio
noise. This undesirable radio noise is generally man-
ifested in the form of ªbuzzing,º ªhissing,º ªpopping,º
ªclicking,º ªcrackling,º and/or ªwhirringº sounds. In
most cases, RFI and EMI radio noise can be sup-
pressed using a combination of vehicle and compo-
nent grounding, filtering and shielding techniques.
This vehicle is equipped with factory-installed radio
noise suppression devices that were designed to min-
imize exposure to typical sources of RFI and EMI;
thereby, minimizing radio noise complaints.
Factory-installed radio noise suppression is accom-
plished primarily through circuitry or devices that
are integral to the factory-installed radios, audio
power amplifiers and other on-board electrical com-
ponents such as generators, wiper motors, blower
motors, and fuel pumps that have been found to be
potential sources of RFI or EMI. External radio noise
suppression devices that are used on this vehicle to
control RFI or EMI, and can be serviced, include the
following:
²Engine-to-body ground strap- This length of
braided ground strap has an eyelet terminal connec-
tor crimped to each end. One end is secured to the
engine cylinder head(s). The other is secured to the
plenum at the exhaust heat shield forward/outer
attaching stud.
²Resistor-type spark plugs- This type of spark
plug has an internal resistor connected in series
between the spark plug terminal and the center elec-
trode to help reduce the production of electromag-
netic radiation that can result in radio noise.
OPERATION
There are two common strategies that can be used
to suppress Radio Frequency Interference (RFI) and
ElectroMagnetic Interference (EMI) radio noise. The
first suppression strategy involves preventing the
production of RFI and EMI electromagnetic signals
at their sources. The second suppression strategy
involves preventing the reception of RFI and EMIelectromagnetic signals by the audio system compo-
nents.
The use of braided ground straps in key locations
is part of the RFI and EMI prevention strategy.
These ground straps ensure adequate ground paths,
particularly for high current components such as
many of those found in the starting, charging, igni-
tion, engine control and transmission control sys-
tems. An insufficient ground path for any of these
high current components may result in radio noise
caused by induced voltages created as the high cur-
rent seeks alternative ground paths through compo-
nents or circuits intended for use by, or in close
proximity to the audio system components or circuits.
Preventing the reception of RFI and EMI is accom-
plished by ensuring that the audio system compo-
nents are correctly installed in the vehicle. Loose,
corroded or improperly soldered wire harness connec-
tions, improperly routed wiring and inadequate audio
system component grounding can all contribute to
the reception of RFI and EMI. A properly grounded
antenna body and radio chassis, as well as a shielded
antenna coaxial cable with clean and tight connec-
tions will each help reduce the potential for reception
of RFI and EMI.
REMOVAL
BED TO CAB
(1) Disconnect and isolate the battery negative
cable.
(2) Remove the attaching bolts and strap (Fig. 10).
Fig. 10 BED TO CAB GROUND STRAP
1 - BED
2 - CAB
3 - GROUND STRAP
4 - MOUNTING BOLTS
DRAUDIO/VIDEO 8A - 9

WIDE OPEN THROTTLE MODE
This is an Open Loop mode. During wide open
throttle operation, the PCM receives the following
inputs.
²Battery voltage
²Crankshaft position sensor
²Engine coolant temperature sensor
²Intake manifold air temperature sensor
²Manifold absolute pressure (MAP) sensor
²Throttle position sensor (TPS)
²Camshaft position sensor signal
During wide open throttle conditions, the following
occurs:
²Voltage is applied to the fuel injectors with the
ASD relay via the PCM. The PCM will then control
the injection sequence and injector pulse width by
turning the ground circuit to each individual injector
on and off. The PCM ignores the oxygen sensor input
signal and provides a predetermined amount of addi-
tional fuel. This is done by adjusting injector pulse
width.
²The PCM adjusts ignition timing by turning the
ground path to the coil(s) on and off.
IGNITION SWITCH OFF MODE
When ignition switch is turned to OFF position,
the PCM stops operating the injectors, ignition coil,
ASD relay and fuel pump relay.
DESCRIPTION - 5 VOLT SUPPLIES
Two different Powertrain Control Module (PCM)
five volt supply circuits are used; primary and sec-
ondary.
DESCRIPTION - IGNITION CIRCUIT SENSE
This circuit ties the ignition switch to the Power-
train Control Module (PCM).
DESCRIPTION - POWER GROUNDS
The Powertrain Control Module (PCM) has 2 main
grounds. Both of these grounds are referred to as
power grounds. All of the high-current, noisy, electri-
cal devices are connected to these grounds as well as
all of the sensor returns. The sensor return comes
into the sensor return circuit, passes through noise
suppression, and is then connected to the power
ground.
The power ground is used to control ground cir-
cuits for the following PCM loads:
²Generator field winding
²Fuel injectors
²Ignition coil(s)
²Certain relays/solenoids
²Certain sensors
DESCRIPTION - SENSOR RETURN
The Sensor Return circuits are internal to the Pow-
ertrain Control Module (PCM).
Sensor Return provides a low±noise ground refer-
ence for all engine control system sensors. Refer to
Power Grounds for more information.
OPERATION
OPERATION - PCM
The PCM operates the fuel system. The PCM is a
pre-programmed, triple microprocessor digital com-
puter. It regulates ignition timing, air-fuel ratio,
emission control devices, charging system, certain
transmission features, speed control, air conditioning
compressor clutch engagement and idle speed. The
PCM can adapt its programming to meet changing
operating conditions.
The PCM receives input signals from various
switches and sensors. Based on these inputs, the
PCM regulates various engine and vehicle operations
through different system components. These compo-
nents are referred to as Powertrain Control Module
(PCM) Outputs. The sensors and switches that pro-
vide inputs to the PCM are considered Powertrain
Control Module (PCM) Inputs.
The PCM adjusts ignition timing based upon
inputs it receives from sensors that react to: engine
rpm, manifold absolute pressure, engine coolant tem-
perature, throttle position, transmission gear selec-
tion (automatic transmission), vehicle speed, power
steering pump pressure, and the brake switch.
The PCM adjusts idle speed based on inputs it
receives from sensors that react to: throttle position,
vehicle speed, transmission gear selection, engine
coolant temperature and from inputs it receives from
the air conditioning clutch switch and brake switch.
Based on inputs that it receives, the PCM adjusts
ignition coil dwell. The PCM also adjusts the gener-
ator charge rate through control of the generator
field and provides speed control operation.
NOTE: PCM Inputs:
²ABS module (if equipped)
²A/C request (if equipped with factory A/C)
²A/C select (if equipped with factory A/C)
²A/C pressure transducer
²Auto shutdown (ASD) sense
²Battery temperature sensor
²Battery voltage
²Brake switch
²J1850 bus (+) circuits
²J1850 bus (-) circuits
²Camshaft position sensor signal
²Crankshaft position sensor
8E - 10 ELECTRONIC CONTROL MODULESDR
POWERTRAIN CONTROL MODULE (Continued)

ENGINE SYSTEMS
TABLE OF CONTENTS
page page
BATTERY SYSTEM......................... 1
CHARGING.............................. 19STARTING............................... 26
BATTERY SYSTEM
TABLE OF CONTENTS
page page
BATTERY SYSTEM
DESCRIPTION..........................1
OPERATION............................2
DIAGNOSIS AND TESTING - BATTERY
SYSTEM.............................2
CLEANING.............................5
INSPECTION...........................5
SPECIFICATIONS........................6
SPECIAL TOOLS
BATTERY SYSTEM SPECIAL TOOLS.......7
BATTERY
DESCRIPTION..........................7
DIAGNOSIS AND TESTING - BATTERY.......7
STANDARD PROCEDURE
STANDARD PROCEDURE - BATTERY
CHARGING...........................8
STANDARD PROCEDURE - BUILT-IN
INDICATOR TEST.....................10
STANDARD PROCEDURE - OPEN-CIRCUIT
VOLTAGE TEST.......................10
STANDARD PROCEDURE - IGNITION-OFF
DRAW TEST.........................11STANDARD PROCEDURE - USING MICRO
420 BATTERY TESTER.................12
REMOVAL.............................13
INSTALLATION.........................14
BATTERY HOLDDOWN
DESCRIPTION.........................14
OPERATION...........................14
REMOVAL.............................14
INSTALLATION.........................14
BATTERY CABLES
DESCRIPTION.........................14
OPERATION...........................15
DIAGNOSIS AND TESTING - BATTERY
CABLES............................15
REMOVAL.............................16
INSTALLATION.........................17
BATTERY TRAY
DESCRIPTION.........................17
OPERATION...........................17
REMOVAL.............................17
INSTALLATION.........................18
BATTERY SYSTEM
DESCRIPTION
A single 12-volt battery is standard factory-in-
stalled equipment on gasoline engine equipped mod-
els. Diesel engine equipped vehicles utilize two
12-volt batteries connected in parallel. All of the com-
ponents of the battery system are located within the
engine compartment of the vehicle. The battery sys-
tem for this vehicle, covers the following related com-
ponents, which are covered in further detail later in
this section of the service manual:²Battery- The storage battery provides a reli-
able means of storing a renewable source of electrical
energy within the vehicle.
²Battery Cables- The battery cables connect
the battery terminal posts to the vehicle electrical
system.
²Battery Holddown- The battery holddown
hardware secures the battery in the battery tray in
the engine compartment.
²Battery Tray- The battery tray provides a
secure mounting location in the vehicle for the bat-
tery and an anchor point for the battery holddown
hardware.
DRENGINE SYSTEMS 8F - 1

For battery system maintenance schedules and
jump starting procedures, see the owner's manual in
the vehicle glove box. Optionally, refer to the Lubri-
cation and Maintenance section of this manual for
the proper battery jump starting procedure. While
battery charging can be considered a maintenance
procedure, the battery charging procedure and
related information are located later in this section of
the service manual. This was done because the bat-
tery must be fully-charged before any battery system
diagnosis or testing procedures can be performed.
OPERATION
The battery system is designed to provide a safe,
efficient, reliable and mobile means of delivering and
storing electrical energy. This electrical energy is
required to operate the engine starting system, as
well as to operate many of the other vehicle acces-
sory systems for limited durations while the engine
and/or the charging system are not operating. The
battery system is also designed to provide a reserve
of electrical energy to supplement the charging sys-
tem for short durations while the engine is running
and the electrical current demands of the vehicle
exceed the output of the charging system. In addition
to delivering, and storing electrical energy for the
vehicle, the battery system serves as a capacitor and
voltage stabilizer for the vehicle electrical system. It
absorbs most abnormal or transient voltages caused
by the switching of any of the electrical components
or circuits in the vehicle.
DIAGNOSIS AND TESTING - BATTERY SYSTEM
The battery, starting, and charging systems in the
vehicle operate with one another and must be tested
as a complete system. In order for the engine to start
and the battery to maintain its charge properly, all of
the components that are used in these systems must
perform within specifications. It is important thatthe battery, starting, and charging systems be thor-
oughly tested and inspected any time a battery needs
to be charged or replaced. The cause of abnormal bat-
tery discharge, overcharging or early battery failure
must be diagnosed and corrected before a battery is
replaced and before a vehicle is returned to service.
The service information for these systems has been
separated within this service manual to make it eas-
ier to locate the specific information you are seeking.
However, when attempting to diagnose any of these
systems, it is important that you keep their interde-
pendency in mind.
The diagnostic procedures used for the battery,
starting, and charging systems include the most
basic conventional diagnostic methods, to the more
sophisticated On-Board Diagnostics (OBD) built into
the Powertrain Control Module (PCM). Use of an
induction-type milliampere ammeter, a volt/ohmme-
ter, a battery charger, a carbon pile rheostat (load
tester), a 12-volt test lamp and/or special service
tools may be required. All OBD-sensed systems are
monitored by the PCM. Each monitored circuit is
assigned a Diagnostic Trouble Code (DTC). The PCM
will store a DTC in electronic memory for any failure
it detects. Always check the PCM for stored trouble
codes before returning the vehicle to service. Refer to
Charging System for the proper charging system test
procedures. Refer to Starting System for the proper
starting system test procedures.
MICRO 420 BATTERY TESTER
The Micro 420 automotive battery tester is
designed to help the dealership technician diagnose a
defective battery. Follow the instruction manual sup-
plied with the tester to properly diagnose a battery.
If the instruction manual is not available, refer to
the standard procedure in this section, which
includes the directions for using the Micro 420 bat-
tery tester.
8F - 2 BATTERY SYSTEMDR
BATTERY SYSTEM (Continued)

MICRO 420 BATTERY TESTER
The Micro 420 automotive battery tester is
designed to help the dealership technician diagnose
the cause of a defective battery. Follow the instruc-
tion manual supplied with the tester to properly
diagnose a battery. If the instruction manual is not
available, refer to the standard procedure in this sec-
tion, which includes the directions for using the
Micro 420 battery tester.
WARNING: IF THE BATTERY SHOWS SIGNS OF
FREEZING, LEAKING OR LOOSE POSTS, DO NOT
TEST, ASSIST-BOOST, OR CHARGE. THE BATTERY
MAY ARC INTERNALLY AND EXPLODE. PERSONAL
INJURY AND/OR VEHICLE DAMAGE MAY RESULT.
WARNING: EXPLOSIVE HYDROGEN GAS FORMS IN
AND AROUND THE BATTERY. DO NOT SMOKE,
USE FLAME, OR CREATE SPARKS NEAR THE BAT-
TERY. PERSONAL INJURY AND/OR VEHICLE DAM-
AGE MAY RESULT.
WARNING: THE BATTERY CONTAINS SULFURIC
ACID, WHICH IS POISONOUS AND CAUSTIC. AVOID
CONTACT WITH THE SKIN, EYES, OR CLOTHING.
IN THE EVENT OF CONTACT, FLUSH WITH WATER
AND CALL A PHYSICIAN IMMEDIATELY. KEEP OUT
OF THE REACH OF CHILDREN.
A battery that will not accept a charge is faulty,
and must be replaced. Further testing is not
required. A fully-charged battery must be load tested
to determine its cranking capacity. A battery that is
fully-charged, but does not pass the load test, is
faulty and must be replaced. Always test battery
using the Micro 420 battery tester before attempting
to replace a battery under the manufactures war-
ranty provisions.
NOTE: Completely discharged batteries may take
several hours to accept a charge. Refer to Standard
Procedures for the proper battery charging proce-
dures.
STANDARD PROCEDURE
STANDARD PROCEDURE - BATTERY
CHARGING
Battery charging can be performed fast or slow, in
terms of time.Slowbattery charging is the best
means of restoring a battery to full potential. Fast
battery charging should only be performed when
absolutely necessary due to time restraints. A battery
is fully-charged when:²All of the battery cells are gassing freely during
battery charging.
²A green color is visible in the sight glass of the
battery built-in test indicator.
²Three hydrometer tests, taken at one-hour inter-
vals, indicate no increase in the temperature-cor-
rected specific gravity of the battery electrolyte.
²Open-circuit voltage of the battery is 12.65 volts
or above.
WARNING: NEVER EXCEED TWENTY AMPERES
WHEN CHARGING A COLD (-1É C [30É F] OR
LOWER) BATTERY. THE BATTERY MAY ARC INTER-
NALLY AND EXPLODE. PERSONAL INJURY AND/OR
VEHICLE DAMAGE MAY RESULT.
CAUTION: Always disconnect and isolate the bat-
tery negative cable before charging a battery. Do
not exceed sixteen volts while charging a battery.
Damage to the vehicle electrical system compo-
nents may result.
CAUTION: Battery electrolyte will bubble inside the
battery case during normal battery charging. Elec-
trolyte boiling or being discharged from the battery
vents indicates a battery overcharging condition.
Immediately reduce the charging rate or turn off the
charger to evaluate the battery condition. Damage
to the battery may result from overcharging.
CAUTION: The battery should not be hot to the
touch. If the battery feels hot to the touch, turn off
the charger and let the battery cool before continu-
ing the charging operation. Damage to the battery
may result.
NOTE: Models equipped with the diesel engine are
equipped with two 12-volt batteries, connected in
parallel (positive-to-positive and negative-to-nega-
tive). In order to ensure proper charging of each
battery, these batteries MUST be disconnected from
each other, as well as from the vehicle electrical
system while being charged.
Some battery chargers are equipped with polarity-
sensing circuitry. This circuitry protects the battery
charger and the battery from being damaged if they
are improperly connected. If the battery state-of-
charge is too low for the polarity-sensing circuitry to
detect, the battery charger will not operate. This
makes it appear that the battery will not accept
charging current. See the instructions provided by
the manufacturer of the battery charger for details
on how to bypass the polarity-sensing circuitry.
8F - 8 BATTERY SYSTEMDR
BATTERY (Continued)

Large eyelet type terminals are crimped onto the
opposite end of the battery cable wire and then sol-
der-dipped. The battery positive cable wires have a
red insulating jacket to provide visual identification
and feature a larger female battery terminal clamp
to allow connection to the larger battery positive ter-
minal post. The battery negative cable wires have a
black insulating jacket and a smaller female battery
terminal clamp.
OPERATION
The battery cables connect the battery terminal
posts to the vehicle electrical system. These cables
also provide a return path for electrical current gen-
erated by the charging system for restoring the volt-
age potential of the battery. The female battery
terminal clamps on the ends of the battery cable
wires provide a strong and reliable connection of the
battery cable to the battery terminal posts. The ter-
minal pinch bolts allow the female terminal clamps
to be tightened around the male terminal posts on
the top of the battery. The eyelet terminals secured
to the ends of the battery cable wires opposite the
female battery terminal clamps provide secure and
reliable connection of the battery to the vehicle elec-
trical system.
DIAGNOSIS AND TESTING - BATTERY CABLES
A voltage drop test will determine if there is exces-
sive resistance in the battery cable terminal connec-
tions or the battery cables. If excessive resistance is
found in the battery cable connections, the connec-
tion point should be disassembled, cleaned of all cor-
rosion or foreign material, then reassembled.
Following reassembly, check the voltage drop for the
battery cable connection and the battery cable again
to confirm repair.
When performing the voltage drop test, it is impor-
tant to remember that the voltage drop is giving an
indication of the resistance between the two points at
which the voltmeter probes are attached.EXAM-
PLE:When testing the resistance of the battery pos-
itive cable, touch the voltmeter leads to the battery
positive cable terminal clamp and to the battery pos-
itive cable eyelet terminal at the starter solenoid
B(+) terminal stud. If you probe the battery positive
terminal post and the battery positive cable eyelet
terminal at the starter solenoid B(+) terminal stud,
you are reading the combined voltage drop in the
battery positive cable terminal clamp-to-terminal
post connection and the battery positive cable.
VOLTAGE DROP TEST
WARNING: MODELS EQUIPPED WITH A DIESEL
ENGINE HAVE AN AUTOMATIC SHUTDOWN (ASD)RELAY LOCATED IN THE POWER DISTRIBUTION
CENTER (PDC). REMOVAL OF THE ASD RELAY
MAY NOT PREVENT THE DIESEL ENGINE FROM
STARTING. BE CERTAIN TO DISCONNECT THE
FUEL SHUTDOWN SOLENOID WIRE HARNESS
CONNECTOR TO PREVENT THE ENGINE FROM
STARTING. FAILURE TO DO SO MAY RESULT IN
PERSONAL INJURY.
The following operation will require a voltmeter
accurate to 1/10 (0.10) volt. Before performing this
test, be certain that the following procedures are
accomplished:
²The battery is fully-charged and tested (Refer to
8 - ELECTRICAL/BATTERY SYSTEM/BATTERY -
STANDARD PROCEDURE).
²Fully engage the parking brake.
²If the vehicle is equipped with an automatic
transmission, place the gearshift selector lever in the
Park position. If the vehicle is equipped with a man-
ual transmission, place the gearshift selector lever in
the Neutral position and block the clutch pedal in the
fully depressed position.
²Verify that all lamps and accessories are turned
off.
²To prevent a gasoline engine from starting,
remove the Automatic ShutDown (ASD) relay. The
ASD relay is located in the Integrated Power Module
(IPM), in the engine compartment. See the fuse and
relay layout label on the underside of the IPM cover
for ASD relay identification and location.
(1) Connect the positive lead of the voltmeter to
the battery negative terminal post. Connect the neg-
ative lead of the voltmeter to the battery negative
cable terminal clamp (Fig. 11). Rotate and hold the
ignition switch in the Start position. Observe the
voltmeter. If voltage is detected, correct the poor con-
nection between the battery negative cable terminal
clamp and the battery negative terminal post.
NOTE: If the vehicle is equipped with two 12v bat-
teries, step #1 must be performed twice, once for
each battery.
(2) Connect the positive lead of the voltmeter to
the battery positive terminal post. Connect the nega-
tive lead of the voltmeter to the battery positive cable
terminal clamp (Fig. 12). Rotate and hold the ignition
switch in the Start position. Observe the voltmeter. If
voltage is detected, correct the poor connection
between the battery positive cable terminal clamp
and the battery positive terminal post.
NOTE: If the vehicle is equipped with two 12v bat-
teries, step #2 must be performed twice, once for
each battery.
DRBATTERY SYSTEM 8F - 15
BATTERY CABLES (Continued)

(2) Disconnect and isolate the remote battery neg-
ative cable terminal.
(3) Remove the battery from the vehicle. Refer to
the procedure in this group.
(4) One at a time, trace the battery cable retaining
pushpins, fasteners and routing clips until the cable
is free from the vehicle.
(5) Remove the battery cable from the engine com-
partment.
INSTALLATION
(1) Position the battery cable in the engine com-
partment.
(2) One at a time, install the battery cable retain-
ing pushpins, fasteners and routing clips until the
cable is installed exactly where it was in the vehicle.
Refer to Wiring for illustrations.
(3) Install the battery in the vehicle. Refer to the
procedure in this group.
(4) Connect the battery negative cable terminal.
BATTERY TRAY
DESCRIPTION
The molded plastic tray battery tray is located in
the left front corner of the engine compartment. On
this model, the battery tray also provides an anchor
point for the anti-lock brake controller, cruise control
servo (if equipped) and the integrated power module
(Fig. 15). The battery hold down hardware is con-
tained within the battery tray. A hole in the bottom
of the battery tray is fitted with a battery tempera-
ture sensor. Refer to Charging System for more infor-
mation on the battery temperature sensor.
OPERATION
The battery tray and the battery hold down hard-
ware combine to secure and stabilize the battery in
the engine compartment, which prevents battery
movement during even the most extreme vehicle
operation. Unrestrained battery movement during
vehicle operation could result in damage to the vehi-
cle, the battery, or both.
REMOVAL
LEFT SIDE
(1) Remove the battery from the battery tray
(Refer to 8 - ELECTRICAL/BATTERY SYSTEM/BAT-
TERY - REMOVAL).
(2) Remove the integrated power module (Refer to
8 - ELECTRICAL/POWER DISTRIBUTION/INTEL-
LIGENT POWER MODULE - REMOVAL).
(3) Disconnect the wire harness retainers from the
battery tray assembly.
(4) Remove the anti-lock brake controller (if
equipped) retaining bolts and support the brake con-
troller with mechanics wire. It is not necessary to
completely remove the anti-lock brake control unit.
(5) Remove the left front wheelhouse splash shiel-
d(Refer to 23 - BODY/EXTERIOR/LF WHEEL-
HOUSE SPLASH SHIELD - REMOVAL).
(6) Mark the location of the cruise servo (if
equipped) and remove the retaining screws. Position
the servo out of the way.
(7) Remove the battery temperature sensor from
the battery tray (Refer to 8 - ELECTRICAL/CHARG-
ING/BATTERY TEMPERATURE SENSOR -
REMOVAL).
(8) Disconnect the purge solenoid from its mount-
ing bracket.
(9) Disconnect the left front fender ground wire.
(10) Remove the remaining battery tray retaining
bolts (Fig. 16).
(11) Remove the battery tray from the vehicle.
RIGHT SIDE
(1) Remove the battery from the battery tray
(Refer to 8 - ELECTRICAL/BATTERY SYSTEM/BAT-
TERY - REMOVAL).
Fig. 15 DR Battery Tray
1 - BATTERY TRAY ASSEMBLY
2 - BATTERY TEMPERATURE SENSOR
3 - ANTI-LOCK BRAKE CONTROLLER MOUNTING LOCATION
4 - INTEGRATED POWER MODULE MOUNTING SANCTION
DRBATTERY SYSTEM 8F - 17
BATTERY CABLES (Continued)

CHARGING
TABLE OF CONTENTS
page page
CHARGING
DESCRIPTION.........................19
OPERATION...........................19
DIAGNOSIS AND TESTING - CHARGING
SYSTEM............................19
SPECIFICATIONS
GENERATOR RATINGS.................20
SPECIFICATIONS - TORQUE - GENERATOR
/ CHARGING SYSTEM..................20
BATTERY TEMPERATURE SENSOR
DESCRIPTION.........................21OPERATION...........................21
REMOVAL.............................21
INSTALLATION.........................21
GENERATOR
DESCRIPTION.........................21
OPERATION...........................21
REMOVAL.............................22
INSTALLATION.........................24
VOLTAGE REGULATOR
DESCRIPTION.........................25
OPERATION...........................25
CHARGING
DESCRIPTION
The charging system consists of:
²Generator
²Electronic Voltage Regulator (EVR) circuitry
within the Powertrain Control Module (PCM). Elec-
tronic Control Module (ECM) for diesel engines.
²Ignition switch
²Battery (refer to 8, Battery for information)
²Battery temperature sensor
²Check Gauges Lamp (if equipped)
²Voltmeter (refer to 8, Instrument Panel and
Gauges for information)
²Wiring harness and connections (refer to 8, Wir-
ing Diagrams for information)
OPERATION
The charging system is turned on and off with the
ignition switch. The system is on when the engine is
running and the ASD relay is energized. When the
ASD relay is on, voltage is supplied to the ASD relay
sense circuit at the PCM (ECM Diesel). This voltage
is connected through the PCM (ECM Diesel) and sup-
plied to one of the generator field terminals (Gen.
Source +) at the back of the generator.
The amount of direct current produced by the gen-
erator is controlled by the EVR (field control) cir-
cuitry contained within the PCM (ECM Diesel). This
circuitry is connected in series with the second rotor
field terminal and ground.
A battery temperature sensor, located in the bat-
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 (ECM
Diesel) to vary the battery charging rate. This isdone by cycling the ground path to control the
strength of the rotor magnetic field. The PCM then
compensates and regulates generator current output
accordingly.
All vehicles are equipped with On-Board Diagnos-
tics (OBD). All OBD-sensed systems, including EVR
(field control) circuitry, are monitored by the PCM
(ECM Diesel). Each monitored circuit is assigned a
Diagnostic Trouble Code (DTC). The PCM will store a
DTC in electronic memory for certain failures it
detects.
The Check Gauges Lamp (if equipped) monitors:
charging system voltage,engine coolant tempera-
ture and engine oil pressure. If an extreme condition
is indicated, the lamp will be illuminated. This is
done as reminder to check the three gauges. The sig-
nal to activate the lamp is sent via the CCD bus cir-
cuits. The lamp is located on the instrument panel.
Refer to 8, Instrument Panel and Gauges for addi-
tional information.
DIAGNOSIS AND TESTING - CHARGING
SYSTEM
The following procedures may be used to diagnose
the charging system if:
²the check gauges lamp (if equipped) is illumi-
nated with the engine running
²the voltmeter (if equipped) does not register
properly
²an undercharged or overcharged battery condi-
tion occurs.
Remember that an undercharged battery is often
caused by:
²accessories being left on with the engine not
running
DRCHARGING 8F - 19