Volvo VNL User manual

Service Manual
Trucks
Group30
New Features
Electrical General
VNL, VNM
PV776-TSP23760/1

Foreword
Thedescriptionsandserviceprocedurescontainedinthismanualarebasedondesigns
andmethodsstudiescarriedoutuptoJanuary1996.
Theproductsareundercontinuousdevelopment.Vehiclesandcomponentsproduced
aftertheabovedatemaythereforehavedifferentspecificationsandrepairmethods.
Whenthisisbelievedtohaveasignificantbearingonthismanual,supplementaryservice
bulletinswillbeissuedtocoverthechanges.
Theneweditionofthismanualwillupdatethechanges.
Inserviceprocedureswherethetitleincorporatesanoperationnumber,thisisa
referencetoanS.R.T.(StandardRepairTime).
Serviceprocedureswhichdonotincludeanoperationnumberinthetitleareforgeneral
informationandnoreferenceismadetoanS.R.T.
Thefollowinglevelsofobservations,cautionsandwarningsareusedinthisService
Documentation:
Note:Indicatesaprocedure,practice,orconditionthatmustbefollowedinordertohave
thevehicleorcomponentfunctioninthemannerintended.
Caution:Indicatesanunsafepracticewheredamagetotheproductcouldoccur.
Warning:Indicatesanunsafepracticewherepersonalinjuryorseveredamagetothe
productcouldoccur.
Danger:Indicatesanunsafepracticewhereseriouspersonalinjuryordeathcouldoccur.
VolvoTrucksNorthAmerica,Inc.
Greensboro,NCUSA
Ordernumber:PV776-TSP23760/1
©1996VolvoTrucksNorthAmerica,Inc.,Greensboro,NCUSA
Allrightsreserved.Nopartofthispublicationmaybereproduced,storedin
retrievalsystem,ortransmittedinanyformsbyanymeans,electronic,me-
chanical,photocopying,recordingorotherwise,withoutthepriorwritten
permissionofVolvoTrucksNorthAmerica,Inc..

Contents
General........................................................................3
ElectricalSystem-VNL,VNM(06.96to02.98)........3
Specifications.............................................................5
ReplacementWireSizes............................................5
Tools............................................................................7
SpecialEquipment.....................................................7
DesignandFunction..................................................9
GeneralCircuitInformation........................................9
CircuitTypes............................................................11
StartingandChargingSystem.................................18
ElectricalPass-ThroughforCabWiring,Powerand
Ground.....................................................................22
SwitchesandControls.............................................23
FuseandRelayLocations.......................................29
LightingSystem........................................................35
Instrumentation.........................................................41
ServiceProcedures..................................................43
GeneralWorkPracticesandCautions....................43
Soldering/WireSplicing............................................46
BatteryCableFusibleLinkReplacement(Battery
toStarter).................................................................47
BatteryCableFusibleLinkReplacement(Ground
Cable).......................................................................48
IgnitionSwitchReplacement....................................50
IgnitionSwitchandHousingReplacement..............52
HornContactsReplacement....................................54
TurnSignal/CCSwitchReplacement......................56
WindshieldWiperSwitchReplacement...................58
Headlight/ParkingLampSwitchReplacement.........60
RoadLamp(FogLamp)SwitchReplacement........62
DimmerControl(dashillumination)Rheostat
SwitchReplacement................................................64
RearSuspensionCabUnloaderControlValve
Replacement............................................................66
LiftAxleControlValveReplacement.......................66
FifthWheelSliderValveReplacement....................66
DifferentialLockoutValveReplacement..................66
AxleLockControlValveReplacement....................66
DashAirSwitchReplacement.................................66
CigarLighterReplacement......................................68
HazardLampSwitchReplacement.........................69
AuxiliaryLightSwitchReplacement.........................69
Dash(LeftSide)SwitchReplacement.....................69
MarkerInterruptSwitchReplacement.....................70
IdleControlSwitchReplacement.............................70
HeatedMirrorSwitchReplacement.........................70
TractionControl(TCS)SwitchReplacement...........70
Dash(RightSide)SwitchReplacement..................71
RadioReplacement(DashMounted)......................72
IgnitionPowerRelayReplacement..........................74
AccessoryPowerRelayReplacement.....................76
DaytimeRunningLampControlModuleReplace-
ment.........................................................................79
CombiRelayReplacement......................................80
PowerWindowSwitchReplacement(RightorLeft)82
PowerMirrorSwitchReplacement..........................83
DigitalClock(Sleeper)Replacement.......................84
SleeperReadingLampSwitchReplacement..........86
SleeperHeaterControlSwitchReplacement..........86
SleeperControlPanelSwitchReplacement............86
WindshieldWiperMotorReplacement....................87
WindshieldWiperLinkageAssemblyReplacement88
OperationNumbers
1

2

Group 30 Electrical System—VNL, VNM General
General
Electrical System - VNL, VNM (06.96 to 02.98)
This manual describes the new electrical features of VN
Series vehicles from introduction 06.96 until 02.98, as well
as general heavy duty electrical service information. It
includes information on new components, circuit types,
controls, connectors and the tools commonly used for
maintenance.
The electrical systems of VOLVO trucks are designed
to withstand the demands of a heavy duty motor truck
under all types of operation. Every effort has been made
to provide trouble-free operation, easy maintenance and
service, and to provide maximum life of the system and
its components.
For more information on VNL and VNM electrical circuitry,
refer to the vehicle electrical schematics.
3

4

Group 30 Electrical System—VNL, VNM Specifications
Specifications
Replacement Wire Sizes
The size of wire used when installing accessories or re-
pairing existing electrical items is dependent on the length
of the wire and power requirements of the accessory. The
chart below can be used to determine the proper wire size
for 12 volt systems.
To use the chart, mark the appropriate length for the wire
being installed in the m/ft column. Also mark the rating in
the amps/watts column. Then draw a line connecting the
mark in the length column to the one in the rating column.
The point where the line crosses the wire size column is
the size of the wire required. If the line crosses the wire
size column between gauge sizes, round up to the next
larger size.
If replacing a wire and the amperage of the circuit is
not known, it can be measured using a digital multimeter
placed in series in the circuit.
EXAMPLE:
A 12 volt hydraulic pump motor is rated at 20 amps.
The complete length of the circuit (power and ground
sides) is approximately 20 feet.
A line drawn from 20 on the length column to 20 on the
rating column crosses the wire size column at the 8.
This indicates that the minimum wire size for the applica-
tion is 8 gauge.
W3001006
Chart for calculating relationship between wire
length, gauge and amperage/wattage
5

6

Group 30 Electrical System—VNL, VNM Tools
Tools
Special Equipment
The following items can be ordered from the vendors listed.
Digital Multimeter (DMM)
A Digital Multimeter (DMM) is one of the most important
tools available for electrical troubleshooting. A multimeter
such as a Fluke 87 is recommended for troubleshooting.
It provides diagnostic capabilities such as current (amper-
age), resistance and voltage tests, as well as specialized
features for automotive troubleshooting. Any circuit can
be tested for continuity or short circuits with a low-reading
voltmeter.
CAUTION
Never use the ohmmeter mode in a powered circuit, or
as a substitute for a voltmeter or ammeter, as damage
to the instrument will result. Use the ohmmeter mode
only when power is removed from the circuit.
When using a multimeter and the value being tested is
unknown, always use the highest scale first and work
down to a mid-scale reading whenever possible. This will
avoid damage to the instrument.
Before using the DMM to measure resistance, check its
calibration by touching the leads together. If there is a
reading other than zero, subtract it from measurements
made with the DMM.
The following tests can be performed with a DMM:
•Current (amperage) check
•Voltage check
•Resistance check
•Diode check
W2001014
Fluke 87 Digital Multimeter
Available from Volvo (P/N 9510060)
or available from your local Fluke dealer
Anti-Static Wrist Strap
A wrist grounding strap must be worn when working on
electronic equipment such as the instrument cluster. This
is to prevent electrostatic discharge (ESD), which can
damage electronic components. To use the wrist strap in
a vehicle, attach the alligator clip to the nearest electrical
ground such as a ground terminal or preferably a ground
stud.
W3000572
Anti-Static Wrist Strap
Available from Kent-Moore (P/N BT-8639-B)
Call 1-800-328-6657
7

Group 30 Electrical System—VNL, VNM Tools
Static Dissipative Mat
Make sure the workbench has an anti-static mat which
is grounded to the nearest electrical outlet when working
on electronic equipment such as the instrument cluster.
When working at the anti-static workbench, always keep
a wrist strap connected to the anti-static mat. Note that
the Static dissipative kit shown includes both an anti-static
mat and wrist strap.
W3000704
Full-Size Type 8501 Static-Dissipative Grounding
Kit, Available from Newark (P/N 46F7444)
Call 1–910–292–7240
Rheostat Removal Tool
The rheostat removal tool is used when removing the dash
rheostat (see
Service Procedures ).
W3000799
Rheostat Removal Tool
Available from Kent-Moore (P/N J-42395)
Call 1-800-328-6657
Window/Mirror Switch Removal Tool
The window/mirror switch removal tool is used to remove
the power window and motor/heated mirror switch con-
nectors (see
Service Procedures ).
W3000800
Window/Mirror Switch Removal Tool
Available from Kent-Moore (P/N J-42396)
Call 1-800-328-6657
8

Group 30 Electrical System—VNL, VNM Design and Function
Design and Function
General Circuit Information
Circuit Malfunctions
In an electrical circuit, current completes a path from its source through the compo-
nent(s), and then back to its source. If it starts at the battery, it must return to the
battery. Current will return to the source even in circuits that are not operating properly.
There are three electrical conditions that cause an inoperative circuit; these conditions
are known as an "open circuit," a "short circuit" and a "grounded circuit."
Open Circuit
Whenever there is a complete break or interruption in the
normal current path, such as a break in wiring from the
source of power to the electrical unit or within the unit
itself, current will not flow. In a circuit, current normally
travels through the wires or cables, to switches and
electrical unit(s), such as the starter solenoid and cranking
motor, through another wire to ground and back to the
source.
A break anywhere along this route results in an open
circuit and the complete loss of power. In a sense, the
break is a very high resistance in the circuit. However,
the symptoms will appear somewhat different than the
typical high resistance because there is no current flow.
An ammeter will not register at all because there cannot
be current flow through an open circuit. A voltmeter,
depending on where it is placed in relation to the open
circuit, may or may not give a reading. The proper use of
meters is covered later in this manual.
Any abnormal resistance reduces the current flow in a
circuit and leaves the unit intermittent or non-functioning.
An open or high-resistance circuit may occur as the
result of a broken wire within the wiring harness, loose
connections at terminals of electrical units, broken wiring
within the units, or poor ground connections between the
unit and ground. Open circuits, depending on the type
and location of the open, can easily create a shorted or a
grounded circuit condition.
W3000489
9

Group 30 Electrical System—VNL, VNM Design and Function
Short Circuit
The term short circuit is used to describe another type of
condition which can develop in electrical circuits or units.
It refers to a circuit that is completed in the wrong way,
such as two bare wires touching each other, so that the
current bypasses part of the normal circuit. Bypassing part
of the normal circuit simply means that the current has
found the path of the least resistance and a higher current
flow, amperage, results. This can result in blown fuses,
open circuit breakers, wiring or component overheat,
burned parts and insulation and, of course, non-working
components. Hot, smelly insulation is always a sign of
trouble. If the wire melts through, there is no electrical
path, so the circuit then becomes open. W3000490
Grounded Circuit
A grounded circuit is similar to a short circuit in that
the current bypasses part of the normal circuit. In this
instance, the current flows directly to ground. This may
be caused by a wire touching ground or part of the circuit
within a unit coming in contact with the frame or housing
of the unit. A grounded circuit may also be caused by
deposits of oil, dirt and moisture around connections or
terminals.
W3000491
10

Group 30 Electrical System—VNL, VNM Design and Function
Circuit Types
Ohm’s Law
Current is the flow of electrons through a conductor, and
is measured in amperes. Voltage (measured in volts) is
the force or pressure which pushes the current through
the conductor. Resistance is opposition to current flow,
and is measured in ohms (
 ).
Ohm’s Law describes the relationship between voltage
(V), current (I) and resistance (R):
V=IxR
I=V
4 R
R=V
4 I
Using this formula, if any two of the values in the formula
are known, the other value can be found. Ohm’s Law tells
us that voltage and current increase proportionally. That
is, when voltage increases, current will also increase if
resistance stays the same. When resistance increases,
current will decrease.
Series Circuits
In series circuits, each electrical device is connected to
other electrical devices insuch a way thatthere is onlyone
path for the current to follow as it flows from the battery,
through the circuit and back to the battery.
W3000492
Typical Series Circuit
Ohm’s Law in Series Circuits
In a series circuit, the total circuit resistance is the sum
of all the resistors in a circuit. In the example below, the
values of the 2 resistors are added together for the total
circuit resistance.
2
 +4  =6  total resistance
Apply Ohm’s Law to find the total circuit current:
I=V
4 R
I = 12 volts
4 6  = 2 amps
Since current is the same at any point in a series circuit, to
find the voltage drop across either resistor, use the above
current value in the formula:
V=IxR
V = 2 amps x 2
 = 4 volts
V = 2 amps x 4
 = 8 volts
The sum of the voltage drops equals the source voltage:
4 volts + 8 volts = 12 volts
W3000567
11

Group 30 Electrical System—VNL, VNM Design and Function
Parallel Circuits
In parallel circuits, electrical devices are connected by
parallel wires. The current divides; part of it flows into one
device, part into another. The voltage remains the same
across each branch of the circuit as though each branch
was connected directly to the source voltage.
With circuits in parallel, each circuit can be switched on
and off by itself since each receives current independently
of the other circuits. The current divides across each
branch of the parallel circuit; the sum of the current in
each of these branches is the total current in the circuit.
The total resistance in parallel circuits is less than any of
the individual resistances. W3000494
Typical Parallel Circuit
Ohm’s Law in parallel circuits
In the circuit below, one resistor is 2  , and the other is
4
 . The source voltage is 12 volts. Current must be found
for each path individually, as follows.
Apply Ohm’s Law to find current across the first resistor:
I=V
4 R
I = 12 volts
4 2  = 6 amps
And for the second resistor:
I = 12 volts
4 4  = 3 amps
Now, to find the total current, add the current from each
of the circuit branches:
3 amps + 6 amps = 9 amps
Using Ohm’s Law, the total circuit resistance can also be
found:
R=V
4 I
R = 12 volts
4 9 amps = 1.33 
Another way to find total resistance in a parallel circuit
with 2 resistors is to divide the product of the 2 resistors
by the sum:
R=(2
 x4  ) 4 (2  +4  )=8  4 6  = 1.33 
Notice that the total resistance of 1.33  is less than either
of the individual resistors in the circuit.
W3000565
12

Group 30 Electrical System—VNL, VNM Design and Function
Series/Parallel Circuits
A series/parallel circuit consists of some components
in series and others are in parallel. In the figure the
components side by side are in series since there is only
one current path. The two circuits above and below each
other are in parallel since there are two current paths.
W3000493
Typical Series/Parallel Circuit
Ohm’s Law in series/parallel circuits
In series/parallel circuits, the easiest way to find a device
value is to look at each part of the circuit separately.
For the example below, first find the resistance in each
branch. The two 2
 and 4  resistors add to give a
resistance of 6
 for this part of the circuit. For the other
2 resistors, 2
 +1  =3  .
To simplify the circuit, think of it as a parallel circuit having
a6
 and 3  resistor.
So, (6
 x3  ) 4 (6  +3  )=18  4 9  =2  total
resistance.
The total circuit current, therefore, is:
I=V
4 R
I = 12 volts
4 2  = 6 amps
The current through each branch can also be determined.
For the branch of the circuit with the 6
 total resistance:
I = 12 volts
4 6  = 2 amps
So, for each resistor in this branch, the voltage drop is
found as follows:
V=IxR
For the 2
 resistor,
V = 2 amps x 2
 = 4 volts
For the 4
 resistor,
V = 2 amps x 4
 = 8 volts
The sum of the voltage drops in a series circuit equals the
source voltage, so 4 volts + 8 volts = 12 volts.
W3000566
13

Group 30 Electrical System—VNL, VNM Design and Function
Typical Circuit Components
Wiring harnesses, wires & connectors
Each circuit uses a wire of a specific size, based on the
current demands for that circuit. The circuit number is
stamped into the insulation every 76 mm (3 in.). This aids
in proper connections and simplifies circuit tracing.
Insulation is cross-linked and flame resistant. White wires
are grounded circuits. Red wires are main power feeds.
Black wires are protected with a fuse or circuit breaker,
etc.
Some wires are grouped together and encased in a split
plastic casing or braided tubing called a loom. This group-
ing of wires is called a harness. Major wiring harnesses
are joined by using a multiple plug and receptacle con-
nector block.
Each harness or wire must be held securely in place by
clips or other holding devices to prevent chafing of the
insulation.
Terminals used throughout the system are Deutsch, Amp,
JAE, KOSTAL and Packard. All terminals are soldered
unless prohibited by the terminal manufacturer.
Circuit protection
To protect wiring and equipment from overloads, circuit
protectors such as fuses, circuit breakers or fusible links
are used.
WARNING
Failure to use proper circuit protection devices in the
vehicle can result in personal injury or damage to the
vehicle. Replace blown fuses only with fuses of the
same rating. Replace fusible links only with proper
replacement parts of the exact gauge and length.
Failure to use proper circuit protection could overload
the circuit, causing possible personal injury and severe
damage to the vehicle.
Fuses
The most common protector in the vehicle circuit is a
fuse. A fuse consists of a fine wire or strip of metal
inside a glass tube or plastic housing. The strip melts and
interrupts the flow of current in the circuit when there is
an overload caused by an unwanted short or ground. The
fuse is designed to melt before the wiring or electrical
components in a circuit can be damaged. Naturally, the
cause must be located or the new fuse will also blow.
Since different circuits handle different amounts of current,
fuses of various ratings are used. Fuses are rated in
amperes. Be sure to replace a blown fuse with a fuse
of the same rating.
A new feature for the VN Series vehicle is the maxi-fuse,
which is designed for a larger amount of current than a
regular fuse.
W3000484
1) Good fuse
2) Blown fuse
14

Group 30 Electrical System—VNL, VNM Design and Function
Fusible links
Fusible links are used to protect high-current circuits
against current overload when there is a short to ground.
The fusible link is a short length of wire that is smaller
in gauge than the wire in the protected circuit. In the
event of an overload the fusible link will melt, breaking the
circuit and preventing damage to the electrical system. If
a fusible link does open, special attention must be paid to
finding and repairing the cause.
Fusible links are used in two locations: two are at the
starter motor on the positive side feeding the cab main
power studs, and one is from ground on the starter motor
to engine ground. The fusible links on the positive side
are 10 gauge cables 120 mm (4.72 in.) in length. On the
ground side, it is an 8 gauge cable.
Diodes
Diodes are used on many of the vehicle’s circuits to
protect and isolate them from voltage surges, which can
occur when a circuit is turned off. Diodes allow voltage to
flow in one direction only, like a one-way check valve.
Circuit breakers
Circuit breakers are optional equipment. SAE Type 2
modified reset circuit breakers are the only type of circuit
breakers approved for use in VNL or VNM vehicles. They
may be used on accessory and ignition circuits only.
Circuit breakers protect a circuit from overload. When an
overload (high current flow) occurs in a circuit, a bimetallic
strip in the breaker is heated. This opens its contact,
temporarily breaking the circuit. When this bimetallic strip
cools down, it remakes the contact.
Type 2 circuit breakers are opened by current overload
and remain open as long as the power is on. A Type
2 circuit breaker keeps the bimetallic strip hot after
tripping by diverting a small amount of current through
a small coil of resistance wire. If power to the circuit
breaker is switched off long enough for the bimetallic
strip and resistance wire to cool down, the breaker will
automatically reset.
When any circuit breaker trips, it should be viewed as
an indication of a possible fault in the circuit. Every effort
should be made to identify and correct the fault if one
exists.
15

Group 30 Electrical System—VNL, VNM Design and Function
Switches and relays
Circuit controls are switches or relays. Switches are
usually at the beginning of a circuit but can be used to
control a ground path. For example, the switch controlling
the headlights is at the power end of the circuit, while the
door switch controlling the dome lightcompletes the circuit
to ground. Relays are remotely controlled switches. They
use a low current signal through a coil to control larger
currents conducted through their contacts.
A new feature used in the VN Series vehicle is the
micro-relay. The micro-relay is smaller in size than a
conventional relay, and the pin arrangement is different
(see illustration).
W3000777
Relay Pin Arrangement and Schematic
W3000778
Micro-relay Pin Arrangement and Schematic
Note: Relays are shown from insertion-side view.
16

Group 30 Electrical System—VNL, VNM Design and Function
Sensors and senders
Many electronic signals used by ECUs and the instrument
cluster are supplied by sensors and senders. A sensor
or sender sends a signal to a control unit, or to the
microprocessor in the instrument cluster. Sensors used
in the vehicle system include the vehicle speed sensor,
the throttle position sensor and Anti-lock Brake System
(ABS) wheel speed sensors.
The vehicle speed sensor is mounted in the transmission
and reads the movementof the teeth on the output shaft.It
is of an inductive type and sends a fluctuating (sinusoidal)
signal to the engine ECU.
An Anti-lock Brake System (ABS) wheel speed sensor is
mounted in each monitored wheel. As the wheel spins,
the sensor sends a fluctuating signal to the ABS ECU,
which the ECU interprets as wheel speed.
W5000602
Anti-lock Brake Wheel Speed Sensor
The transmission oil temperature sender, shown in the
illustration, senses the temperature of the transmission
oil, creating a resistance and sending this signal to the
instrument cluster. The higher the temperature of the oil,
the lower theresistance, and the higherthe readingshown
on the gauge.
W3000813
Transmission Oil Temperature Sender
The engine oil temperature sender functions similarly,
but sends engine oil temperature information to the
instrument cluster. The fuel sender, mounted in the fuel
tank, transmits the fuel level to the instrument cluster.
17

Group 30 Electrical System—VNL, VNM Design and Function
Starting and Charging System
Battery Power Supply
Power is supplied from the batteries to the starter sole-
noid, then from the starter solenoid battery post via wires 1
and 1-A. (Note that each of these wires contains a fusible
link.) Wire I feeds cab main power stud 1, and 1-A feeds
cab main power stud 2.
The batteries also supply constant power to the alternator
via the starter solenoid. The starter solenoid post is con-
nected directly to the battery by wire 8, which senses the
battery voltage and energizes the alternator for charging
the batteries.
•Stud 1 powers the Battery Maxi-fuse bus bar. From
this bus bar a Battery Maxi-fuse feeds 1-F to the the
fuse bus bar for fuse positions 21–24.
Also from the Battery Maxi-fuse bus bar, a Battery
Maxi-fuse feeds 1-D to the fuse bus bar for fuse
positions 17–20. Another Battery Maxi-fuse feeds 1-
C to the fuse bus bar for fuse positions 25–32.
Also from stud 1, wire 1-E goes to the Accessory
Power Relay.
•From stud 2, wire 1-A goes to the Ignition Power
Relay. From wire 1-A, 1-B sends battery power to
bus bar fuse positions 41–48. W3000827
APass-through for main cab wiring
Main Cab Electrical Pass-Through and Ground
Studs (driver side engine compartment)
Accessory Supply
•From fuse 15, wire 243–A supplies constant battery
power to the ignition switch.
•When the ignition switch is switched to the ACCES-
SORY position, the 195 wire energizes the Acces-
sory Power Relay. The relay supplies power to wire
195–A for the bus bar for the Accessory fuse posi-
tions 33–40.
•Ground wire 0R-N provides a ground connection
from the Accessory Power Relay to the Ignition
Power Relay. From the Ignition Power Relay, ground
connection 0R-M goes to a passenger side interior
ground stud (see section in this manual on
Electrical
Pass-through for Cab Wiring, Power and Ground
).
18