Volvo Service Manual, Section 3(37) Component Wiring Diagram

Chassis Number 503 through to 4853

How to read the diagrams2
Electrically operated main switch, E-T-A (electrical cut-out)5
Manual main switch at batteries (manual cut-out)6
Electrically operated main switch, Bosch, (battery cut-out)6
Alternators 60 A, 80 A, 120 A7
Starting heater, starter, cold start, stop device, engine compartment, reversing lights, air dryer8
Differential lock, level control, overdrive, retarder9
Brake lights, lighting switch, full beams, dipped beams, tachometer, temperature gauge, fuel gauge10
Coolant level, blinkers, windscreen washers, windscreen wipers11
Indicator and warning lights12
Electrical components, location14

Table of Contents


This service manual contains the component wiring diagrams for the B 10M chassis electrical system.

The advantage of component wiring diagrams is that they show separately the wiring for each electrical component. This makes it much easier to understand how the component functions, what it is that influences the function, where possible faults may arise, etc. These component diagrams are, therefore, particularly suitable when tracing faults in the electrical system.

Page 1

How to read the diagrams

The line running across the top of the diagram with digits on it denotes the "+" feed. The digits serve as cross references for the various circuits. The line running along the bottom of the diagram denotes the "-", that is, connection to earth.

Note that relay-operated circuits have been drawn in two parts: one, where the relay contacts are shown separately; the other, where the relay coils are shown in the respective operating circuits. Example: relay 316 for the starter motor (page 6, cross-reference line 27) is operated by the coil in the circuit with cross-reference number 64 (see page 8).

The cable numbering, the symbols for the connections, etc., are the same as those on the general wiring diagram for the bus chassis, see Service Bulletin 3-37-18.

The following symbols are used.

Symbol, RelayRelaySymbol, FuseFuseSymbol, Circuit breakerCircuit breakerSymbol, ResistanceResistance
Symbol, Closing contactClosing contactSymbol, Break contactBreak contactSymbol, Electric MotorElectric MotorSymbol, Slip ringsSlip rings
Symbol, Warning/indicator lightsWarning/indicator lightsSymbol, LightLightSymbol, CoilCoilSymbol, DiodeDiode
Symbol, Magnetic release/Thermal releaseMagnetic release
Thermal release
Symbol, BuzzerBuzzerSymbol, Solenoid valveSolenoid valve
Symbol, Cross-referenceRefers to cross-reference line 28Symbol, Reference marksExample of reference marks between the various parts of main wiring diagram

Symbol, Wiring connections, Joints, Relay Contacts


Wiring example
48Cross-reference line
53Component number (fuse holder)
:3Fuse No. 3
16Reference to cross-reference line 16
28and 28
312Component number (relay, starting heater)
20"B"14Connector 20 marked B, connection 14
14Cable number
800Component number (starting heater)
528Component number (indicator light, pre-heating

How to read a wiring diagram when fault tracing

With all fault tracing in the electrical system, it is important that the circuits are traced systematically.

First check the voltage at the component where the fault is suspected. In this example we have chosen to examine the start circuit to the starter motor. At the check, there should be voltage at the starter motor "50" when the starting key is switched to the start position.

If there is voltage at "50", the fault must be in the starter motor or in the electrical circuit between the battery-starter motor-earth, engine.

If the is no voltage at "50", continue the fault tracing with the help of the diagram on pages 3 and 4.

If the fault tracing is to show results, the batteries must be in good condition, cable shoes properly tightened, etc. Moreover, the main switch (at the batteries) must be on.

Page 2

A.Is there voltage at the starting switch terminal "30"?
-If not, examine the connectors and fuses shown in the diagram. Start with fuse (2) in the fuse holder (53) and fuse (1) in the fuse holder (60). If these are without faults, check the voltage at connector 32 marked C, terminal 1 and at connector 20 marked A, terminals 29 and 30. If there is still no voltage, examine the connections at the main switch and at the batteries.
-If there is voltage at "30" continue to the next point in the fault tracing below.
Note:Concerning the location of the fuse holder, etc., see list on pages 14 to 16.
B.Trace the circuit from starting switch "50" to relay "start inhibitor 345". This relay is not activated until the alternator starts to charge. The relay breaks the start circuit so that the starter motor cannot be engaged after the engine has started.
 To check whether the relay is closed when making attempt to start pull out the relay a bit from the relay holder so that the voltage at ""87A"" on the relay can be checked. If there is voltage at "87A", when the starting key is at the start position, there is no fault in the starting key or in the circuit up to relay 345.
 The breaking function can be checked by providing "A" on the charging regulator with voltage "24A". The terminal "87A" should then be without voltage when attempting to start.

Page 3

C.Does the relay "start position 354" function when the starting key is at the start position?
-Let an assistant feel with a finger on the relay. If the relay does not function, first check the relay and then the fuse (11) in the fuse holder (60). Check the voltage at connection 6 marked D, terminal 4 (see arrow). If there is no voltage there, go back in the circuit towards the starting switch and check the connectors. If there is voltage, check the voltage at connector 6 marked D, terminal 1. If there is no voltage at terminal 1 check the circuit for "N" position transmission.
-Relay 354 functions, continue to the next point below.
D.Does the relay "operating magnet starter motor 316" function when the starting key is at the start position?
-If not, check relay 316 and for any breakage in the relay's operating circuit.
-If the relay functions, check the fuse (3) in the fuse holder (53) and the fuse (3) in the fuse holder (54).
The starter motor circuits have now been examined. The rest of the main wiring diagram can be read in exactly the same way, that is, the circuits are traced step by step until the wiring for the electrical component in questions has been fully covered.

Page 4

Electrically operated main switch, E-T-A (electrical cut-out)

Note: The connectors underlined in red are intended to be used when connecting up the various electrical components for the body. (See also pages 6, 8 to 11 and 13.

Page 5

Page 6

Page 7

Page 8

Page 9

Page 10

Page 11

Indicator and warning lights

526GREEN retarder
530GREEN electrically heated rear view mirrors
500GREEN direction indicators
504BLUE fullbeams
545YELLOW "Stop"
544RED engine compartment temperature
546RED doors
543RED luggage compartment lids (with buzzer)
507RED air pressure (with buzzer)
554YELLOW coolant temperature (with buzzer)
540YELLOW lube oil level
505YELLOW battery charging
503YELLOW lube oil pressure
565YELLOW coolant level
508RED parking brake
528YELLOW preheating (starting heater)
532YELLOW reversing lights
512YELLOW optional (not wired)
542RED door brake
541YELLOW temperature transmission oil

Page 12

Page 13

Location of electrical components on B10M chassis

The letter and digit in brackets after the component indicate where the component is situated on the general wiring diagram (see Service Bulletin 3-37-18).

ComponentPositionPart number
6Connector 6-unit"D" under dashboard "2", body builder connection, under dashboard 
12Connector 12-unit"1" and "3" body builder connection under dashboard, "C" under dashboard 
20Connector 37-unit"A" and "B" under pedal plate, two unmarked in Conn. box. battery box 
32Circuit card, electrical distribution centre (F3)Depending on body builder1132086-8
33Circuit card, indicator/warning lights (A2)Dashboard1135032-9
34Connector (F3)At steering column/pedal plate under dashboard347714-8, -715-5, -716-3
37Terminal, earth connection--
52Fuse holder 2-unit (G1)Battery box inside connection box941111-7
53Fuse holder 3-unit (G3)Battery box inside connection box1139899-7
54Fuse holder 4-unitBattery box inside connection box1191766-3
60Fuse holder 14-unit (F1)In electrical distribution centre-
100To switch, lighting (K2)Connector 12 marked "3"-
101Stalk, fullbeams and dipped beams (B1)Steering column1130268-4
115Switch, instrument panel light (Cl)Dashboard1504570-1
119Stalk, windscreen wipers (B1)Steering column1130267-6
120Stalk, windscreen washer (B1)Steering column1130267-6
123To switch, rear view mirror (K2)Connector 12 marked "2"-
125Switch, exhaust brake (C3)Pedal plate1584341-0
126Switch, diff. lock wheels, rear (C2)Instrument panel1578734-4
144Switch, main switch (G2)Connection box, battery box or placed by body builder, e.g. at entrance door240315-2 or 72306-4
147Stalk, direction indicators (B1)Steering column1130268-4
149Switch, horn (B1)Steering wheel hub-
150Switch, starting switch (B2)Steering column1190222-8
151Switch, retarder (D2)Dashboard1135426-3
153Switch, automatic preheating (C1)Dashboard1135401-6
159Switch, bulb failure warning light (C1)Dashboard1135401-6
160Switch, stop engine (C2)Dashboard1135401-6
161Switch, cold start (C1)Dashboard1135401-6
175Switch, level control (Cl)Dashboard1137176-2
176Switch, overdrive (splitter) (C3)On gear lever 
195Shift selector Allison (K1)Dashboard 
200Break contact, warning light, parking brake (Cl)Pedal plate1578928-2
202Break contact, warning light, oil pressure (H2)Engine 
207Closing contact, indicator light, diff. lock wheels, rear (J3)Rear axle1266085-8
215Closing contact, warning light, tachograph (C2)In tachograph 
216Closing contact, stop lights (C1)Pedal plate-
217Closing contact, reversing lights (J2)Gearbox1136651-5
223Slip contact, horn (Al)Steering wheel hub 
233Closing contact, warning light, coolant (K2)On pipe for expansion tank-
238Closing contact, thermal (H2)In engine compartment above engine1581232-4
251Break contact, splitter (K1)On top of gearbox1130035-7
305To relay, reversing lights (K2)Connector 12 marked "1" 

Page 14

ComponentPositionPart number
306Relay, fullbeams(E2)Electrical distribution centre1504951-3
307Relay, dipped beams (E2)Electrical distribution centre1504951-3
309Relay, parking lights (E2)Electrical distribution centre1504951-3
312Relay, starting heater (F3)In connection box battery box1577376-5
316Relay, solenoid starter motor (G1)In connection boxy battery box1504951-3
320Relay, main switch (G2)In connection box battery box (battery cut~out)240143-8
322Relay, coolant level (E2)Electrical distribution centre1501618-1
323To flasher device (K2)Connector 12, marked "1"-
325Step relay, fullbeams and dipped beams (E3)Electrical distribution centre355535-6
328Charging regulator (G2)In connection boxy battery box (120 A gen. in alternator)60A 367603-8; 80A 367604-6
331Relay, retarder (J2)In connection box retarder (frame member in front of retarder)Connection box 1190720-1, circuit card 1190721-9
333Time relay, automatic preheating (E3)Electrical distribution centre1578630-4
334Relay, horn (E1)Electrical distribution centre1504951-3
342Main switch (at batteries)Connection box, battery box (electrical switch)1190533-8 or 1190534-6
345Relay, start inhibitor (E1)Electrical distribution centre1504951-3
349Relay, battery charging warning light (E1)Electrical distribution centre1504951-3
351Relay, cold start (G1)Connection box, battery box1504951-3
354Relay, starting position (E1)Electrical distribution centre1504951-3
361Relay, main switch operation (F2)In connection box, battery box ~used with battery cut~out)1504951-3
383Relay, engine compartment fan (G1)In connection box, battery box (used with battery cut~out)1504951-3
384Relay, splitter (C3)Behind dashboard1504951-3
400To bulb, fullbeams and dipped beams (K2)Connector 6 marked "2"-
408To bulb, parking light (left front) (K2)Connector 6 marked "2"-
409To bulb, parking light (right front) (K2)Connector 6 marked "2"-
431Bulb, instrument panel light (K2)Instrument panel182034-9
500Indicator light, direction indicator, tractor (B2)Control lamp panel symbol disc 1 1) lens green2)Component 500 to 546 excluding 523 Bulb holder 1504690-7 Bulb 182034-9
503Warning light, oil pressure engine (B3)Control lamp panel symbol disc 3 lens yellow
504Indicator light, fullbeams (B2)Control lamp panel symbol disc 1 lens blue
505Warning light, battery charging (B3)Control lamp panel symbol disc 3 lens yellow
507Warning light, service brakes (B2)Control lamp panel symbol disc 3 lens red
508Warning light, parking brake (B3)Control lamp panel symbol disc 3 lens red
512Warning light, temperature torque converter (B3)Control lamp panel symbol disc 4 lens yellow
523Indicator light, tachograph (C2)In tachograph 
526Retarder (B2)Control lamp panel symbol disc 1 lens green
528Indicator light, starting heater (B3)Control lamp panel symbol disc 4 lens yellow
530Indicator light, heated rear view mirror (B2)Control lamp panel symbol disc 1 lens green
532Indicator light, reversing lights (B3)Control lamp panel symbol disc 4 lens yellow
540Warning light, oil level (B3)Control lamp panel symbol disc 31) lens yellow2)
541Warning light, gearbox temperature (B3)Control lamp panel symbol disc 4 lens yellow
542Warning light, door stop (B3)Control lamp panel symbol disc 4 lens red
543Warning light, lids luggage and engine (B3)Control lamp panel symbol disc 2 lens red
544Warning light, engine compartment temperature (B2)Control lamp panel symbol disc 2 lens red
545Warning light, STOP bus stop (B2)Control lamp panel symbol disc 1 lens yellow
546Warning light, opening doors (B2)Control lamp panel symbol disc 2 lens red
547Central warning for indicator and warning lights (D1)Dashboard1130162-9
554Warning light coolant temperature (B2)Control lamp panel symbol disc 2 lens yellow
555Warning light coolant level (B3)Control lamp panel symbol disc 3 lens yellow
601Solenoid valve, differential lock wheels, rear (J1)Compressed air output behind battery box1576728-8

Page 15

ComponentPositionPart number
603Solenoid valve, engine stop (J1)Compressed-air output behind battery box1576728-8
629Solenoid valve, cold start (J1)On engine
642Solenoid valve, overdrive (splitter) (J1)Compressed air output behind battery box
643Solenoid valve, level control (J2)Compressed air output behind battery box1576728-8
650To windscreen wiper motor (K2)Connector 12 marked "1"1576728-8
651To windscreen washer motor (K2)Connector 12 marked "1"15766728-8
654Starter motor (H2)On engine1576728-8
655Alternator 60A/80A (H3)In front of front axle
660Alternator with charging regulator 120A (H3)In front of front axle367814-A
666Engine compartment fan (H2)In engine compartment
EL motor1191735-8
brush holder1191736-6
700Speedometer (C2)On dashboard(see parts catalogue)
701Tachograph (C2)On dashboard(see parts catalogue)
703Tachometer (C1)On dashboard1507170-2
704Air gauge (C1)On dashboard1578020-8
706Thermometer (C1)On dashboard1578118-0
707Fuel gauge (C1)On dashboard1502183-5
753Speed sender, engine (H1)On engine157818-35
756Temperature sender, coolant (H1)On engine1578134-7
757Fuel level gauge sender (H1)In fuel tank(see parts catalogue)
758Speed sender, gearbox (H1)On gearbox1507899-1
762Oil temperature sender, gearbox (H1)On pipe in gearbox-
763Level sender, oil (H2)In tube oil tank engine1131929-0
800Starting heater (F3)On engine-
806Resistance (C1)Under dashboard (lighting power)330445-8
807Eddy retarder control (D2)Hand control on dashboard foot control-footbrake valve1130956 (hand control)
810Electrically heated air dryer (J2)In air dryer lower section-
850For horn (K2)Connector 12 marked "1"-
853Buzzer 1D11Under dashboard (warning)-
903Diode (F2, D2)Connector 12 marked "C" for eddy retarder-
908Shunt (G2)In connection box battery box ~80A alternator~-
950Electrical coils, eddy retarder (J2)In eddy retarder-
1000Cable harness, dashboardDashboard-
1002Cable harness, tachograph (C2)Dashboard-
1011Cable harness, direction indicators (A1)Dashboard-
1012Cable harness, windscreen wipers (A1)Dashboard-
1014 Cable harness, starting switch (A2)Dashboard-
1030Cable harness, engine (H1)Engine-
1033Cable harness, eddy retarder (D3)Under dashboard-
1035Cable harness, differential lock (B3)Under dashboard-
1039Cable harness, overdrive 1B31Under dashboard-
1040Cable harness, frame (G1)From pedal plate to connection box, battery box-
1052Cable harness, dashboard electrical distribution centre (D1)From dashboard to electrical distribution centre-
1053Cable harness, electrical box (G1)In connection box, battery box-

Note: Fuses5A942545-58A948843-8Fast fuses (Circuit breakers)
 16A948845-380A239148-075A 242185-7 (alternator 60A)
 150A1134337-3  150A 352808-0 (80A alternator alt. 120A)
 160A1190797-9(main switch at batteries)
 150A1134337-3(main switch at batteries)

Page 16