Cat 312c Diagr Elec

 

Description

 

 

Component

Wire Wire Number  Color 

 

Description

Accessory Circuits (Continued)

Power Circuits

Schematic Location

Machine Location

D-3

1A

Sens o r - Water Sepa or r atorLeve rator l

4F

Socket - 12V 7A

A-12

2

Socket - 12V 7A

 A/C Switch Panel  Actuator - Engine Gove rnor rnor

A-7

 Air Heater

 

Component

 

Schematic Location

Machine Location

J-12

36

E-6

11A

E-6

28

1 01

R D

Battery +

5 78

BU

Washer -Aux.

1 03

R D  

Monitor 

5 86

BR

Aux. Hydraulic - Close

 Alarm - Action

D-2

2A

Solenoid- 1Pump - 2Pump Exchange1

D-7

31

1 05

R D

Key Switch

5 90

G Y

Wiper Switch TOIntermediate Module

 Alarm - Travel

E-12

3

Solenoid- 1Pump - 2Pump Exchange2

D-7

32

 Alternator

C-12

4

S ol en oi d- A /C C u l ct h

B1 - 2

19

C-5

5

S ol en oi d- D ou bl eA ct o i n

D7 -

33

J-12

6

S oel n o i d- F l ow L i m i t P r es s u re

B-9

G 8-

1 09

R D

Alternator B+

R D

5 92

BU

DC/DC Converter Power Output

RD

ATCH ConverterMemory

 Antenna

Timer RelayB+

 A513

PU

Main PowerRelay Output

 A537

PK

Seat Heater 

1E

S ol e n oi d- H am me r

A 4-

40

O R

Panel B+

 A579

OR

Wiper Motor +

B er ak er - A tl er na ot r

G1 - 0

2E

S oel n o i d- H y dr a u l i cL o k c

A-9

10F

R D

Forward Horn

 A580

BR

Wiper Motor -

C on tr ol - E ng ni e/ Pu mp

F -8

3E

S oel n o i d- P o we rS hfit C o nt r ol

A-7

5F

1 15

R D

Cab Lamp

 A581

GN

Wiper Motor Raise

Converter

D-6

27

S ol en oi d- Q ui ck C ou pl er

C -9

11F

1 18

G Y  

Wiper/Washer 

 A582

PU

Wiper Motor Stop

C o n e v tr er - 12V 7A

J 6-

1D

S ol en oi d- R ot at eC CW

A5 -

37

1 19

PK

Cab Fan

 A584

BU

Front Window LimitSwitch To Wipercontrol

C on ve tr er - 1 2 V 2 x 7A

H6 -

29

S ol e n oi d- R ot at eC W

A 5-

38

1 20

Y L

12V 7AConverter 1

 A586

OR

Wiper SwitchTo Wiper Control

1 23

W H

Seat Heater 

 A588

GN

Safety SolenoidRelay To Solenoid

B-2

7

G N

A/C

C 53 7

GN

A/C PhotoSensor +Signal

Horn

1 24

Joystick

H-1

7B

S ol en oi d- T hu mb C o l se

A4 -

1 29

BU

Cigar Lighter 

C 53 8

OR

A/C PhotoSensor -Signal

Joystick

J-2

2C

S ol en oi d- T hu mb O pe n

A4 -

D

1 35

BU

Switched ConverterOutput

C 56 0

OR

Left Rear Speaker 

Lamp - Boom

C-2

8

Sole n oid- Travel noid e l Speed Change

A-9

8F

1 43

BR

Alternator Regulator 

C 56 6

PK

Left RearSpeaker (Common)

Lamp - Cab

9

Speaker

1 47

PU

Beacon and Heated Seat

C 56 9

YL

Second DC/DC Converter Power Output

Lamp - Chassis

10

Switch - 1Pump- 2PumpExcha n ge nge

1 49

R D

Boom Lamp

E 55 4

PK

A/C Controller To A/CCompressor Clutch Lighting Circuits

Battery Bl o c k- T e r m i n al

G 1-

1B

S oel n o i d- S i n g l eA cito n1

D-7

34

Fuse Block

H -11

4E

S oel n o i d- S i n g l eA cito n2

D-7

35

S oel n o i d- S wni gB r ak eC a nc e l

A-9

9F

F-1

J 1- 2

23

J-1

3D

Quick Coupler  Neutral StartLimit Switch

6 07

PK

Flood Lamp- Front

BU

L o we r W i pe r W / a s he r  

6 15

YL

Cab Flood Lights

RD

Neutral StartLimitSwitch

6 16

BU

Boom Flood Lights

1 60

M ot or - L o w er W pi er

1 68

PU R D

Refueling Lamp

PK

Backup/Monitor Control

R D

Product Link

R D

A/C Blower 

5A

Switch - Backup

F-1

6A

S wi tc h- B al de P re ss ur e

Motor - Fan

F-6

21A

S wi tc h- C oo al nt L ev el

J1 - 2

20

M oot r- A T CH L ow e rW a h ser

J-1 2

11

S wi ct h- D si co nn e ct

G1 - 1

19E

J1 -

2D

Meter - Service

D-1

Monit or

6 45

R D

Boom Lam Relay

6 46

R D

Delay Timer Lamp SwitchATCH

M ot or - R ef ue il ng P um p

A2 -

 A623

BU

Right Cab FloodLamp Switch ToRelay

Motor - St a rter

B-12

Motor - Washer

J-12

7 63

BU

Torque Converter Switch

Motor - Wiper

E -1

Control Circuits

14A

S wi ct h- A ri C el an e r Switch - Aux.Hydra u licPress ulic u re ure

G N

1 72

12A

3A 4A

O R

1 75

F-6 D-5

E-6

154

1 69

This indicates that the component does not have a wire connected to ground. It is grounded by being fastened to the machine.

D-1

152

G -2 H1 -

T

21

S wtic h- E n g i n eO i lL ev e l

A-1 2

42

S wtic h- E n g i n eO i lP r e s s ur e

A-1 2

12

S wi ct h- H am me rF oo t

J 1-

13

S wtic h- H a mm e rP r e s s ur e

A-4

41

7A

S wtic h- H a mm e rP r e s s ur e

H-1

4D

J-2

1C

22 48

R D

Aux. Circuit

Coupler DisengageSolenoid

26

PU

Switch - Horn

9A

12V 7AConverter 2

D-5

BU

YL

Engine Speed +

S wtic h- H y dr a ul i cO i lF itle r

7 88

R el ay - B oo mL a mp

J 1- 1

5E

S wtic h- H y dr a ul i cO i lL ev e l

A-6

G N

Aux. Circuit

 A718

PU

Start AidCoolant Sensor Signal

R e l a y-C a b Lam p

H 1- 1

7E

S wtic h- I m pl e m e n tP r es s u re

D - 12

25

1 84

R D

Engine Pump Control

 A755

PK

Throttle Switch #1

R el ay - C ha ss si L am p

J1 - 1

6E

S wtic h- J o ys tci k P r e s s ur e

J-3

5D

1 89

R D

Engine GovernorActuator 

 A756

BU

Throttle Switch #2

Relay - Heater

8E

S wi tc h- L ow er W as he r

D3 -

15A

1 91

W H

Power WindowControl

 A757

GY

Throttle Switch #3

Relay - Horn

9E

S wi ct h- L ow er W pi er

D 3-

16A

 A758

BR

Throttle Switch #4

R eal y- H y dr a u l i cL o k c S oel no i d

2 00

BK

Main Chassis

 A761

PU

Electronic PumpControl ThrottleGround

Ground Circuits

Radio - AM/ FM

D-5

Radio - AM/ FM

J-7 H -11 H - 11

1 0E

A-6

7F

A-5

11E

S wtic h- M e d i u mL ni eP r es s u re

J-1

6D

12 E

S wtic h- N e ut r al S t ar t L i m it

H-2

7D

R e l a y-R e f uel nig 1

A- 3

43

S wtic h- O n eT o u c hL o wI del

G-1

3B

A- 3

BK

Operator Monitor Return

2 10

BK

Converter Output(24/12V)

 A768

44

BK

Battery -

Switch Panel

2 29

 A769

H 7-

18E

Sw ti ch P a n e l- A C /

2 35

BK

Engine Pump Control Ground

 A770

PK

Electronic Pump ControlBypass Switch To Resistor 

R e l a y-R o t at eC W

H 7-

17E

S wi tc h- Q ui ck C ou pl er

E1 -

A

F 77 3

OR

Governor Acceleration

R el ay - S ta tr C on tr ol

J1 - 0

13E

S wi ct h- R ef ue il ng L ev el

A 5-

47

F 77 4

WH

Governor Deceleration

Relay - St art

G -7

14E

S wi ct h- R ef ue il ng S a t tr

A 3-

45

K 77 6

GN

Start RelayControl To Alternator 

R el ay - T hu mb C ol se

H6 -

E

S wi ct h- R ef ue il ng S o t p

A 3-

46

Switch - Single/Do u bleActio uble n Exchange

D-5

19A

Basic Machine Circuits

PU

Electronic Pump Control Engine SpeedGround

BU

Pump ControlValve #1 +

GY

Pump ControlValve #2 -

R e l a y-R e f uel nig 2 R e l a y-R o t at eC CW

3 04

W H

Start Relay Output

3 06

G N

Start Relay ToStart Relay Diode

3 07

O R

Key Switch ToNeutral Start Relay

K 77 7

GY

Implement Pressure Switch

3 08

Y L

Main PowerRelay Coil

M 73 4

BR

Travel ModeSwitch

3 09

G Y

Alternator Regulator Terminal

M 73 6

BU

Governor Command

3 10

PU

Start Aid Switch To Start Aid Solenoid

M 73 7

WH

Front Flow controlValve Solenoid

3 20

R D

Horn Relay To Horn Switch

M 73 9

YL

Solenoid Return 2

Send e r - HydraulicOilTemp er e ratu eratu re re

Travel Alarm Cancel

S en so r- A /C H ea e t rP ho o t

H6 -

E

Relay - Timer

J-10

15E

Sw ti ch - S e at H e at er

J 7-

16E

S wi ct h- S pe ed C ha ng e

R e s sit or - B a c kup

BR

Backup Alarm Lamp Travel Alarm

M 74 1

GY

G Y

Forward Horn

M 74 2

PU

AEC Model Switch

Sensor o r - AIH CoolantTemperature

W H

Fuel Pump Power 

T 71 3

GN

Thumb Open Circuit

S en so r- F ue lL e v el

PK

Fuel PumpRelay Cut-out

T 71 4

BU

Thumb Open Circuit

R D

Key Switch toEngine Shutdown Solenoid

T 71 5

WH

3 30

Y L

Start Control RelayTo Start Relay

T 71 6

PK

Thumb Close Circuit

3 65

Y L

Fuel PumpRelay to Switch

8 77

YL

Air Heater 

Monitor Circuits

8 92

BR

Cat DataLink +

8 93

G N

Cat DataLink -

4 03

Alternator (R) Term

G N

Thumb Close Circuit

Operator Monitor Oil Pressure (LowSet)

K 84 3

GN

Stem 3Extend Switch

Operator Monitor Action Alarm

K 84 4

GY

Stem 4Extend Switch

BU

Operator MonitorCoolant Flow

K 84 7

PU

Stem 3Retract Switch

4 30

BU

Operator MonitorAir Filter 

K 84 8

WH

Stem 4Retract Switch

4 87

O R

Hydraulic Oil Flow Switch

K 84 9

YL

ATT Stem 1

4 91

PK

Hydraulic Oil Temperature Sensor 

K 85 1

BU

ATT Stem 3

4 92

G Y

Coolant TemperatureSensor Signal

K 85 2

GN

ATT Stem 4

4 95

G N

Fuel LevelSignal

K 85 8

YL

Stem 3Control Valve A

4 96

W H

Operator Monitor PanelHydraulic Oil Level

K 86 2

GY

Stem 3Control Valve B

C 46 8

BU

Engine Oil Level

K 87 1

WH

Pump Exchange Solenoid

E 47 2

GN

ATT 12VSensor Supply

K 87 2

OR

Single/Double Action Exchange Solenoid

E 47 3

GY

Stem 1Modulation

K 87 9

GN

E 47 4

OR

Stem 2Modulation

C 98 7

H 46 5

GN

Travel AlarmCancel Indicator 

G 97 6

BU

Water Separator Sensor 

H 46 6

BU

AEC Mode Indicator 

K 90 4

GN

Pump Discharge- Signal

4 05

G Y

4 10

W H

4 12

H 46 7

Travel Mode indicator 1

WH

H 47 6

WH

5 01

K 90 6

Joystick Pressure Switch

K 90 7

Accessory Circuits

RD

GN BU

Switch - Starter S wi tc h- T ra ve lP e r ss ur e

1F

S wi tc h- U nd er W ni do wL m i ti

E1 -

10A 16 17

C-12 A 6-

+Battery

Swing BrakeSolenoid - Signal

OR

Engine PumpControl PS Valve -

Wiper - Front (Low)

L 96 9

WH

Engine PumpControl PS Valve +

PU

Washer -Front

L 97 1

GN

Travel Pressure Switch

PU

Radio Speaker - Left

L 97 2

BU

Low IdleSwitch

5 09

W H

Radio Speaker -Left (common)

L 97 3

GN

Fine Swing ControlRelay To SolenoidValve

5 11

BR

Radio Speaker - Right

L 97 5

PK

Start AidControl Lamp 1 Output

5 12

G N

Radio Speaker -Right (Common)

L 97 6

GN

Excavator Fuel Pump Switch

5 30

O R

Washer -Right

M 94 7

OR

Rotate CW Relay

5 35

BU

2 0A

S wi ct h- W ni do wL m i ti

F1 -

18 A

U n i t- Ai rC o n d it oi n e r

G 5G-5

1

U ni t- H ea e t rC on rt ol

J 7-

20 E

Unit - IND

G -1

A-1 2

18

Wiper C ontrol

D-2

A = Inside of cab.

1 2

36

8A

 A

49

28 B

51

16

31

4 2

15 21

27

5

3

19

26

9 8

34

32 24

25

52

7

33

22

Connector Number 

14 1

7

12

40  41

 

Schematic Location

8

G-11

21E 21

C ON N 2

F-11

22E 22

C ON N 3

F-11

23E 23

C ON N 4

F-10

24E 24

C ON N 5

F-10

25E 25

C ON N 6

F-10

C ON N 7

G- 9

C ON N 8

G- 9

53

54 55

10

42  43  44  45

47 F

46

30

3 2E 32

100 119

Engine oil pressure is low F u el l e ve l i s l o w

9D

171

Engine oil level is low

21A 21

179

Abnormal battery charge (Charging is abnormal)

C ON N 17

E-7

4 9

C ON N 18

G-7

E

232 235

Waterseparator draining demand Hydraulic oil level is low

C ON N 19

F-5

2 2A 22

236

Hydraulic oil filter si clogged

C ON N 20

F-4

2 3A 23

C ON N 21

J -3

5 0

237 272

O v er l oa d w a rn i ng Air filter is clogged

600 862

Hydraulic oil overheat Special filter is clogged

863

Automatic greasing failure

BU

Hammer Foot Switch To HammerSolenoid

C ON N 22

J -3

M 96 2

YL

Rotate CCW Relay

C ON N 23

H-3

T 96 7

YL

Pump DischargeMean Pressure

C ID

1

C om po ne nt

Data valid but above normal m al operational range. Data valid but below normal m al operational range.

2

Data erratic, intermittent,or incorrect.

0091

Throttle Position Signal

3

Voltage above normal or shorted high.

0096 0110

Fuel Level Sensor  Engine Coolant Temperature Sensor 

4

Voltage below normal or shorted low.

5

Currentbelownormalor open circuit. c uit.

0167 0168 0190

Alternator n atorCharging Sensor  SystemVoltage Engine Speed Sensor 

6

Currentabovenormalor grounded circuit.

7

Mechanical system not responding properly.

8

Abnormal frequency,pulsewidth,or period.

0254 0271

Electronic Control Module Action Alarm

9

Abnormal update.

10

Abnormal ate a r te of change.

0286

Engine OilPressure Switch

11

Failure mode notidentifiable.

0374

SwingBrakeSolenoid

12

Bad deviceor component.

0376

TravelAlarm

13

Out of calibration a tion.

0581

PowerShiftSolenoid

0586

Engine Speed Dial Switch

0587

Engine Governor n or PositionSensor 

0588

MonitoringSystem

0598 0600

TravelSpeedSolenoid Hydraulic OilTemperatureSensor 

1161

Front Hydraulic PumpPressure Sensor 

1162 1525

Rear Hydraulic PumpPressure Sensor  Straight TravelSolenoid

1The

FMI is a diagnostic code that indicates what type of failure has occurred.

8

34  35

37 38 39 40 41

52

49 24 25

4 19

12

31 18

22

32

21

17 57

14

5 1

H-2

1 1D 11

H-2

1 2D 12

C ON N 26

C-3

5 2

C ON N 27

B-3

5 3

C ON N 28

A-3

C ON N 29

5 4

A-3

5 5

C ON N 30

F-2

2 4A 24

C ONN 31

G-1

8B

C ON N 32

F-1

2 5A 25

C ON N 33

F-1

2 6A 26

C ON N 34

B-2

5 6

CONN 35

 A-5

57

F-5

 A

F-3

 A

CONN 38

F-3

 A

CONN 39 CONN 40

H-3 H-3

B

CONN 41

E-1

 A

CONN 37 2

1 0D 10

C ON N 24 C ON N 25

CONN 36

47 23

15  16

Fuel filter is clogged

G-7 D-5,D-6

M 95 4

0

95

3 1E 31

G-7 J-6,H-6

C ON N 16

Wiper - Aux. (Park)

1

3 0E 30

G-7

C ONN 15

Switch ToWiper Switch

9

Insufficient levelof coolant

2 9E 29

Wiper - Aux. (Low)

5

Abnormal battery charge (Voltage to powersupply low) Abnormal battery charge (Voltage to powersupply high)

59

G-8

Y L

F a il u re D e sc r ip t io n

D es cr p i it on C o ol a nt O v er h e at

43 50

C ONN 11 C ONN 13

Event Codes For Engine / Pump Control E ve nt C od e 17

28E 28 1 2F

PK

Failure Mode Identifiers (FMI)1

27E 27

B-9

5 76

F M IN o .

26E 26

G- 8

5 75

Component Identifiers (CID1) Module Identifier (MID2) Engine/Pump Control System (MID No. 069)

4

11

B

The connectors shown in this chart are for harness to harness connectors.

27 26 7 56 54  55 53 42  43  44  45  46

1 28

33

10

Connectors that join a harness to a component are generally located at or near the component. See the Component Location Chart. 3

2

30 3

6

20 11 13 36

29

50 51

D

Typicalrepresentationof aSure-Seal connector. The plug and receptacle contain both pins and sockets.

Printed in U.S.A.

34E 34

C ON N 9 C ONN 10

C ONN 14

17

37  38  39 57

1 2

Machine Location

C ON N 1

C ONN 12

56

35

18

Typical representation of a Deutsch connector. The plug contains all sockets and the receptacle contains all pins.

Connector Location

9 48

E

200-BK-14

© 2004 Caterpillar   All Rights Reserved

D = Backside of platform. E=Aroundrelaypanel. F=Inside ofhydraulicpump.

C

50 23

11 6

Receptacle 2

Volume 1: CAB And CHASSIS

6B

29 13

20

CircuitNumber  WireGauge Identification Plug Ground Connection

Pin or Socket Number 

1

Unit - Heater

2F 3F

105-9344

1

325-PK-14

Single Wire Connector 

Component Part Number  Fuse

AA

5B 24

E1 -

B = Inside of right console. C = Inside of left console.

Wire, Cable, or Harness  Assembly Identification

4B

D -1 2

A-7

Sen s o r- E n g i n eS p e dP i ck u p

WireColor 

 A

17A

A-7

Machinelocationsarerepeatedforcomponentslocatedclose together.

Harness And Wire Symbols

Pin   Socket

A

Sensor o r - PumpDisch a rgePress 1 arge

Swing Brake Solenoid - +Battery

L 96 8

G N

5 06 5 08

G -1

Solenoid - A solenoid is an electrical component that is activated by electricity. It has a coil that makes an electromagnet when current flows through it. The electromagnet can open or close a valve or move a piece of metal that can do work.

13A

Sensor o r - PumpDisch a rgePress 2 arge

Double Action Solenoid  

G3 -

14 15

A-6

H1 -

3 25

D 3-

C-12

S ea tW ti hS ea tH ea e t r Send e r - En er g ineCoolantTemperature gine

3 23

3 26

D 3-

R el ay - T hu mb O pe n

3 22

3 21

D-2

Relay (Magnetic Switch) - A relay is an electrical component that is activated by electricity. It has a coil that makes an electromagnet when current flows through it. The electromagnet can open or close the switch part of the relay.

39

S wtic h- M e d i u mL ni eP r es s u re

J-8 H1 - 1

2 01

 A762

312C Excavator  Electrical System CBA1-1645 FDS1-332

6F

R el ay - N eu rt alS a t tr

Relay - Main

Sender- A component that is used with a temperature or pressure gauge. The sender  measures the temperature or pressure. Its resistance changes to give an indication to the gauge of the temperature or pressure.

2B

1 80

7 80

Reed Switch - A switch whose contacts are controlled by a magnet. A magnet closes the contacts of a normally open reed switch; it opens the contacts of a normally closed reed switch.

8D

1 79

1 76

Circuit Breaker  Symbol

Flow Symbol

Normally closed switch that will open with an increase of a specific condition. No circle indicates that the wire cannot be disconnected from the component.

D

Lamp - Dome

1 51

Level Symbol

This indicates that the component has a wire connected to it that is connected to ground.

Lighter - C giar

1 50

Chassis Lamp

30

En g i n eS p e e d D ai l

B-2

T

Temperature Symbol

Normally open switch that will close with an i ncrease of a specific condition (temp-press-etc.). The circle indicates that the component has screw terminals and a wire can be disconnected from it.

1 13

1 12

RENR5515-02 October 2004 Pressure Symbol

1 14

1 10

Electrical Schematic Symbols And Definitions

Component Location

WireDescription Wire Wire Number  Color 

7

48

6 1 5 10

Related Electrical Service Manuals Title

The CID is a diagnostic code that indicates which component is faulty.

Engine/Pump Control:

2

The MID is a diagnostic code that indicates which electronic control module diagnosed the fault.

Form Number  157-3165

 

9

12

8

RENR3814

 AREA F

Machine Harness Connector And Component Locations

     2      0       5      1     5     5     R     N     E     R

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