curso cat 966h-972h stmg

SERV7105-09September 2005Vol. 9, No. 1

TECHNICAL PRESENTATION

966H AND 972H WHEEL LOADERSINTRODUCTION

New Product Introduction(NPI)

GLOBAL SERVICE LEARNING

966H AND 972H WHEEL LOADERS INTRODUCTION

AUDIENCE

Level II - Service personnel who understands the principles of machine system operation,diagnostic equipment, and procedures for testing and adjusting.

CONTENT

This presentation provides new and different New Product Introduction (NPI) information forthe 966H and 972H Wheel Loaders. This presentation may be used for self-paced and self-directed training.

OBJECTIVESAfter learning the information in this presentation, the technician will be able to:

1. locate and identify the new components on the 966H and 972H Wheel Loaders; and2. explain the operation of the new components in the systems.

REFERENCES

TIM "966G/972G Wheel Loaders - Power Train" SERV2658TIM "966G/972G Wheel Loaders - Steering and Brake Systems" SERV2659TIM "966G/972G Wheel Loaders - Command Control Steering System" SERV2660

Estimated Time: 2 HoursIllustrations: 38Handouts: 5Form: SERV7105-09Date: 09/05

© 2005 Caterpillar Inc.

TABLE OF CONTENTS

INTRODUCTION ........................................................................................................................5

SIMILARITIES AND DIFFERENCES .......................................................................................6

MACHINE APPEARANCE.........................................................................................................7

ENGINE......................................................................................................................................13

IMPLEMENT HYDRAULIC SYSTEM....................................................................................19Implement Hydraulic System - HOLD.................................................................................19Pump Control Valve - Engine OFF ......................................................................................22Pump Control Valve - STANDBY........................................................................................24Pump Control Group - Upstroke ..........................................................................................25Pump Control Valve - Constant Flow Demand ....................................................................26Pump Control Valve - Maximum System Pressure ..............................................................27Pump Control Valve - Maximum System Pressure with Added Flow Demand ..................28Tilt Control Valve - HOLD...................................................................................................32Implement Hydraulic System - DUMP ................................................................................33Implement Hydraulic System - DUMP ................................................................................37Implement Hydraulic System - RAISE ................................................................................39Implement Hydraulic System - FLOAT ...............................................................................41Implement Hydraulic System -TILT BACK AND RAISE ..................................................43Implement Hydraulic System - RIDE CONTROL AUTO...................................................45Calibrations and Adjustments for Implement Hydraulic System.........................................47

STEERING SYSTEM ................................................................................................................49

FAN AND BRAKE HYDRAULIC SYSTEM ...........................................................................50Calibrations and Adjustments for Fan and Brake System....................................................54

NEW TOOLING/SKILLS REQUIRED FOR SERVICE ..........................................................55

CONCLUSION...........................................................................................................................56

HYDRAULIC SCHEMATIC COLOR CODE...........................................................................57

HANDOUTS...............................................................................................................................58

POSTTEST .................................................................................................................................61

POSTTEST ANSWERS .............................................................................................................63

SERV7105-09 - 3 - NPIVol. 9, No. 1, 2005

NOTES

SERV7105-09 - 4 - NPIVol. 9, No. 1, 2005

INTRODUCTION

The 966H and 972H Wheel Loaders have been updated to enhance performance and to meet theTier III emissions regulations. The serial number prefixes of the "H" Series Medium WheelLoaders are as follows:

966H Wheel LoaderAurora A6D

Gosselies A6G

Sagami A6J

972H Wheel LoaderAurora A7D

Gosselies A7G

Sagami A7J

1

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SIMILARITIES AND DIFFERENCES

The most significant change to the H Series Medium Wheel Loaders is the machineconfiguration. Conventional (Hand Metering Unit (HMU)) steering with electrohydraulicimplement controls is the standard configuration. Command Control Steering (CCS) will beoffered as an attachment.

The engines in the "H" Series Medium Wheel Loaders are changing to Tier III emissionscompliant Caterpillar engines with ACERT™ technology.

The implement hydraulic system is changing to a Proportional Priority, Pressure Compensated(3PC) system. The brake and fan systems are now combined, utilizing a single pump.

Machine appearance has changed with the hydraulic tank being mounted behind the cab andtwo service centers located under the cab on the both sides of the machine. The operator’sstation features new style switches.

SERV7105-09 - 6 - NPIVol. 9, No. 1, 2005

FEATURESConfiguration/Attachments Engine

Machine Appearance

Power Train

X

X

XDIFFERENT SIMILAR SAME

X

X

X

X

SIMILARITIES AND DIFFERENCES

Operator's Station

Monitoring System

XHydraulic System

Cooling Package

MACHINE APPEARANCE

The top of the cooling package (1) is lower and the entire cooling package is wider on the 966Hand 972H Wheel Loaders. Two service centers, right side (2) and left side (not shown), havebeen added to the machine. The service centers provide a central location for diagnostic tests,filters, and other components used to service the machine.

3

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1

2

The following components are located on the left side of the machine below the cab:

- Battery disconnect switch (1)

- Hood actuator switch (2)

- Breaker panel (3)

- Battery box (4)

- Ground level shutdown switch (5)

- Power train oil fill cap (6)

- Power train oil level sight gauge (6)

The following breakers are located in the breaker panel:

- 105 ampere for the alternator

- 30 ampere for the unswitched buss

- 20 ampere for the hood actuator

- 50 ampere for the starter

- 80 ampere main for the system

4

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4

5

6

7

The hydraulic tank (1), the hydraulic tank breaker relief valve (2), and the hydraulic tank fillcap (3) are now located behind the cab.

5

SERV7105-09 - 9 - NPIVol. 9, No. 1, 2005

1 2

3

The service center is located on the right side of the machine below the cab. The followingcomponents are located in the service center:

- Case drain filter (1)

- Hydraulic oil fluid sampling valve (2)

- Hydraulic systems kidney loop filter (3)

- Brake system accumulators (4)

- Power train oil fluid sampling valve (5)

- Power train oil filter (6)

- Ecology drain for the hydraulic tank (7)

6

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45

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7

The following remote pressure taps are located inside the panel on the front side of the servicecenter:

- Transmission reverse clutch (1)

- Transmission forward clutch (2)

- Transmission fourth speed clutch (3)

- Transmission third speed clutch (4)

- Transmission second speed clutch (5)

- Transmission first speed clutch (6)

- Steering pump outlet pressure (7)

- Torque converter inlet pressure (8)

- Brake system accumulator pressure (9)

- Transmission lubrication pressure (10)

- Transmission pump outlet pressure (11)

- Torque converter outlet pressure (12)

- Steering cylinder rod end grease zerks (13)

- Rear axle oscillation bearing grease zerks (14)

7

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345

6

7 8 9

10 11 12

13

14

The automatic lubrication reservoir (arrow) is located on the platform on the right side of themachine.

NOTE: The automatic lubrication system will NOT be available at first ship of themachine.

8

SERV7105-09 - 12 - NPIVol. 9, No. 1, 2005

ENGINE

The 966H Wheel Loader is equipped with the Caterpillar C11 ACERT™ engine, serial numberprefix RSX. The displacement of the C11 ACERT™ engine is 11.1 liters with a rated grosspower of 283 hp. The performance test specification for the C11 ACERT™ engine in the 966HWheel Loader is 0K4835.

The 972H Wheel Loader is equipped with the Caterpillar C13 ACERT™ engine, serial numberprefix MHX. The displacement of the C13 ACERT™ engine is 13.1 liters with a rated grosspower of 307 hp. The performance test specification for the C13 ACERT™ engine in the 972HWheel Loader is 0K4841.

9

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The following electrical components are located on the right side of the machine on the engine:

- Engine oil pressure sensor (5)

- Air intake pressure sensor (2)

- Inlet air temperature sender (3)

- A4E4 Engine ECM (4)

- Atmospheric pressure sensor (1)

- Crankshaft speed timing sensor (6)

- Camshaft speed timing sensor (7)

The A4E4 Engine ECM features a 120 pin connector and a 70 pin connector.

10

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1

6

7

2

3

4

5

The following components are found on the fuel filter bases on the right side of the machine:

- Fuel priming pump switch (1)

- Electric fuel priming pump (2)

- Fuel pressure sensor (3)

- Fuel temperature sender (4)

- Differential fuel pressure switch (5)

- Air bleed valve (6)

- Primary fuel filter and water separator (7)

- Secondary fuel filter (8)

11

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6

78

The following components are located on the left side of the machine on the engine:

- Bracket for ether start aid bottle (2)

- Muffler (3)

- Turbocharger with wastegate (4)

- Engine oil fluid sampling valve (5)

- Engine oil filter (6)

Also shown is the hydraulic tank and sight gauge (1) located behind the cab. The radiator toptank and sight gauge (4) are located on the left side of the machine, just above the cooling fan.

12

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67

The hydraulic oil cooler (1) and the air conditioner condenser coil (2) are located at the rear ofthe machine. These two components swing out to allow the removal of debris from the coolingpackage. The radiator (3) and the Air To Air AfterCooler (ATAAC) (4) are also located at therear of the machine. The fuel tank filler cap (not shown) is also located in this area.

13

SERV7105-09 - 17 - NPIVol. 9, No. 1, 2005

1

2

3 4

The following components are located on the front of the engine:

- Coolant temperature sender (1)

- Automatic belt tensioner (2)

- Alternator drive pulley (3)

- Air conditioner compressor drive pulley (4)

- Serpentine drive belt (5)

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15

IMPLEMENT HYDRAULIC SYSTEM

Implement Hydraulic System - HOLD

The "H" Series Medium Wheel Loaders are now equipped with a Proportional Priority, PressureCompensated (3PC) implement hydraulic system. The 3PC hydraulic system is load sensingwith a signal duplication valve, signal relief valve, pressure compensator valves, pressuredifferential relief valve, pressure reducing valve, and a resolver network. Also, the 3PC valvehas anti-drift solenoid valves for the lift and tilt functions.

The implement control valve is a closed-center valve. The 3PC hydraulic system will sense ademand for a change in flow and the implement pump will upstroke or destroke to provide theflow.

The machine may also be equipped with an optional auxiliary function. The auxiliary section isinstalled between the ride control valve and the cover manifold.

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When the engine is started and the implement control levers are in the HOLD position, theimplement pump supplies standby oil flow to the 3PC valve group.

The oil flows into the inlet manifold and is divided into two paths. The supply path for theimplements flows through the inlet manifold into the tilt section where the flow path is dividedagain. One path flows to the tilt stem and is blocked. The second path flows to the lift controlsection, to the ride control section, to the optional auxiliary section, and to the cover manifold.Within the cover manifold, the oil flows to both the pilot pressure reducing valve (PRV) andthe differential pressure relief valve. The differential pressure relief valve maintains adifference between the load sensing pressure and the pump supply oil pressure of 3000 kPa(435 psi). When all of the control valves are in the HOLD position, the implement pump is atlow pressure standby. The differential pressure relief valve maintains the minimum pressurefor low pressure standby. The standby pressure is directed to the pilot pressure reducing valve,and the pilot pressure reducing valve provides a regulated pilot oil pressure to activate thecontrol valves as needed.

The pilot oil flows from the PRV through the check valve to the pilot accumulator and thehydraulic lockout solenoid valve. If the wheel loader is equipped with the optional CommandControl Steering (CCS), the oil flow will be shared by the implement pilot system and thesteering pilot system.

The hydraulic lockout solenoid valve is in the CLOSED position until the hydraulic lockoutswitch in the cab is activated. When the solenoid valve is energized, the solenoid valve opensand pilot oil flows to the various implement function solenoid valves.

The second path of oil in the inlet manifold flows through the screen to the signal duplicationvalve. The signal duplication valve uses the pump supply oil to duplicate the signal from thehighest pressure in the resolver network. When all implement control valves are in the HOLDposition, there is no load sensing signal in the resolver network. With no load sensing pressurepresent, the implement pump is at low pressure standby.

SERV7105-09 - 20 - NPIVol. 9, No. 1, 2005

The implement pump is a variable displacement piston pump. The pump control valve (1)controls the angle of the swash plate (not shown). The implement pump supplies oil flow forthe implement hydraulic system, the implement pilot system, and the optional CCS pilotsystem.

Maximum angle stop adjustment screw (2) is used to adjust the maximum upstroke position ofthe actuator piston in the pump control valve (1).

16

SERV7105-09 - 21 - NPIVol. 9, No. 1, 2005

1 2

17

Pump Control Valve - Engine OFF

This illustration shows the pump control group components with the engine OFF. Theswashplate pin connects the actuator piston is connected to the pump swashplate (not shown).The bias spring moves the actuator piston and the pump swashplate to maximum angle. Thepump control valve group consists of a load sensing spool assembly, which consists of a loadsensing spool and a load sensing sleeve. The load sensing spool is moved up or down bydifferent signal pressures pushing on the piston on each end of the spool. The pump systempressure piston receives an internal signal pressure equal to pump system pressure. The loadsensing piston receives a load sensing signal from the implement hydraulic control valve, whichis equal to the highest work pressure. The signal relief valve (located in the implement controlvalve) limits the maximum load sensing signal to the load sensing piston.

Pump system pressure is directed through the orifice on the right side of the control valve groupto the spring chamber in the upstroke end of the actuator piston and the center lands of the loadsensing piston.

SERV7105-09 - 22 - NPIVol. 9, No. 1, 2005

LS Signal fromWork Port

To ImplementControl Valve

Signal ReliefValve

Bias Spring

Pump Upstroke

Orifice

Actuator Piston

Swashplate PinLoad Sensing Piston

Load Sensing Sleeve

Load Sensing Spool

Pump System Pressure Piston

Margin Spring

Maximum Angle StopAdjustment Screw

Set Screw

LoadSensing

AdjustmentScrew

Pump

PUMP CONTROL VALVEENGINE OFF

The adjustment screw at the top of the actuator piston is used to the adjust maximum angle ofthe swashplate. The set screw at the top of the load sensing spool is used to hold the loadsensing sleeve in position. The adjustment screw at the bottom of the load sensing spool isused to adjust the load sensing margin pressure for the pump. The spring at the bottom of theload sensing spool is the margin pressure spring.

SERV7105-09 - 23 - NPIVol. 9, No. 1, 2005

18

Pump Control Valve - STANDBY

When the engine is started, pump flow goes to the closed-center control valves in theimplement control valve group. The flow is blocked in the implement control valve. Pressurein the system increases, and the pump system pressure is directed to the top end of the actuatorpiston. Pump system pressure on top of the pump system pressure piston moves the piston andload sensing spool down against the force of the margin spring. The spool moves down untilthe upper opening of the spool opens a path around the load sensing spool to drain.

The opening to drain must open sufficient to provide a pressure differential across the orifice.With reduced pressure on the lower end and full pressure on the top of the actuator piston, theactuator piston moves the swashplate pin toward minimum angle.

In STANDBY, the pump is delivering minimum flow to compensate for leakage in the pump,for leakage in the implement control valve, and for the operation of the pump control valve.

SERV7105-09 - 24 - NPIVol. 9, No. 1, 2005

LS Signal fromWork Port


Signal ReliefValve

Bias Spring

Pump Destroke

Orifice

Actuator Piston

Swashplate PinLoad Sensing Piston

Load Sensing Sleeve

Load Sensing Spool


Margin Spring


Set Screw

LoadSensing

AdjustmentScrew

Pump

PUMP CONTROL VALVESTANDBY

19

Pump Control Group - Upstroke

When the control lever or levers are moved to activate one or more implements, a load sensingsignal, equal to the highest work port pressure, is directed to the lower end of the load sensingpiston. The combined forces of the load sensing piston and the margin spring push the loadsensing spool up until the center land on the load sensing spool closes the drain passage. Theupward movement of the load sensing spool continues until the lower opening of the spoolopens a path to the two metering ports. Pump system oil flows through the lower opening ofthe load sensing spool to the spring chamber of the actuator piston. The combined force on thethe larger diameter of the actuator piston and the spring pushes the actuator piston and theswashplate pin up, increasing the swashplate angle to increase pump flow.

SERV7105-09 - 25 - NPIVol. 9, No. 1, 2005

LS Signal FromWork Port


Signal ReliefValve

Bias Spring

Pump Upstroke

Orifice

Actuator Piston

Swashplate Pin

Load Sensing Piston

Load Sensing Sleeve

Load Sensing Spool


Margin Spring


Set Screw

LoadSensing

AdjustmentScrew

Pump

PUMP CONTROL VALVEUPSTROKE

20

Pump Control Valve - Constant Flow Demand

When the flow demand is met, the force developed by the pump system pressure on top of thepump system pressure piston is equal to the force developed by the load sensing signal on theload sensing piston plus margin spring. When the forces are equal, the pump flow is constantand the load sensing spool is in the CENTER position.

The pump flow remains constant until a change in the flow demand occurs.

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Pump Control Valve - Maximum System Pressure

This illustration shows the pump control valve with the load sense pressure at signal relief withone function activated.

When the work port pressure increases to the setting of the signal relief valve, the valve opensto limit the signal pressure to the bottom of the load sensing piston. Pump system pressure willincrease to overcome the combination of forces on the bottom of the load sensing piston. Theload sensing spool moves down to open the actuator piston spring cavity to drain. The pumpsystem pressure moves the actuator piston and swashplate pin towards minimum angle. Thepump destrokes to minimum flow.

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Pump Control Valve - Maximum System Pressure With Added Flow Demand

This illustration shows the pump control valve with the load sense pressure at signal relief.When an additional function is activated, the pump system pressure slightly decreases. Withless pressure on top of the pump system pressure piston, the force on the bottom of the loadsensing piston moves the load sensing spool up. The load sensing spool restricts the flowthrough the upper opening to drain. The increased pressure on the larger area of the actuatorpiston plus the bias spring pushes the actuator piston up. The pump upstrokes to meet theadded flow demand.

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This photo shows a front view of the implement control valve in the loader frame. Thefollowing components can be seen in this view:

- Pressure differential relief valve (1)

- Head end solenoid valve (ride control) (2)

- Signal relief valve (3)

- Tilt anti-drift valve (4)

- Rod end solenoid valve (ride control) (5)

- Ride control balance solenoid valve (6)

- Pilot pressure reducing valve (7)

- Pilot accumulator (8)

- Pilot supply pressure tap (9)

- Lift cylinder head end pressure tap (10)

- Lift cylinder head end pressure sensor for Payload Control System and Autodig (10)

- Hydraulic lockout solenoid valve (12)

23

SERV7105-09 - 29 - NPIVol. 9, No. 1, 2005

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The following components can be seen from the left rear of the control valve:

- Tilt anti-drift valve (1)

- Signal relief valve (2)

- Signal duplication valve (3)

- Return to tank port (4)

- Supply port from pump (5)

- Signal line to pump (6)

- Tank line (7)

- Screen (8)

- Tilt back pilot solenoid valve (9)

- Tilt back pilot (10)

- Tilt cylinder rod end line relief (11)

- Ride control balance solenoid valve (12)

- Rod end solenoid valve (ride control) (13)

24

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The following components are located on the right side of the implement control valve:

- Tilt cylinder rod end line relief (1)

- Lift anti-drift valve (2)

- Line to manual lower valve (3)

- Tank line (4)

- Ride control relief valve (5)

- Line to ride control accumulator (6)

- Raise pilot solenoid valve (7)

- Dump pilot solenoid valve (8)

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Tilt Control Valve - HOLD

With the tilt control valve in the HOLD position, the springs on each end of the control spoolkeep the spool centered. The control spool blocks the flow of pump supply oil to the pressurecompensator valve.

The bridge passage is open to tank through the internal passage in the control spool and there isno oil flow to the resolver valve. With no oil flow to the resolver network, there is no signal tothe signal duplication valve and the signal pressure to the pump control valve is matching theoil pressure in the resolver network. The implement pump is supplying low pressure standby.

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Implement Hydraulic System - DUMP

When the tilt lever is moved to the DUMP position, the Implement ECM energizes the dumpproportional solenoid and the tilt anti-drift valve. As the control valve initially shifts to the left,and there is pressure in the rod end of the tilt cylinder, the pressure goes around the controlspool to the bridge passage. The pressure in the bridge passage goes to the resolver networkand to the signal duplication valve to upstroke the implement pump. The pressure also goes tothe spring chamber in the center of the pressure compensator valve. The lower half of thepressure compensator valve shifts down to block the oil flow from the bridge passage to thefeeder passage.

As the tilt control spool continues shifting to the left, pump supply oil flows around the centerland on the control spool to the feeder passage. Oil pressure in the feeder passage lift thepressure compensator valve up. Pump flow goes through the opening in the lower end of thecompensator valve to the bridge passage. From the bridge passage the pump flow goes aroundthe right end of the control spool into the work port to the rod end of the tilt cylinder.

Return oil from the head end of the tilt cylinder flows around the tilt anti-drift valve and the leftend of the control spool to the tank port.

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Three compensators are shown in various states in this illustration. The pressure compensatorvalve for valve "A" is in HOLD. The circuit with the highest workport pressure keeps theresolver valve closed.

The circuit with the highest work port pressure regulates the oil flow through all activatedcontrol valves. The highest work port pressure is directed through the ball resolver network tothe pump control valve as the load sensing pressure.

When a high pressure circuit is activated as shown for valve "C", the control spool is shiftedand pump supply oil enters the feeder passage below the pressure compensator valve. Pressureincreases and the pressure compensator valve moves up. When the valve moves up, supply oilenters the bridged passage of the control valve. Supply oil in the bridged passage enters thesignal network sending the work port pressure to the signal duplication valve.

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The work port oil pressure goes to the signal duplication valve. The signal duplication valve isa shock absorber. The valve uses the work port pressure signal and the pump system pressuresignal to generate a stabilized load sensing signal which is sent to the pump control valve. Thepump control valve directs a pressure signal to the actuator piston to UPSTROKE the pump.The increased flow lifts the pressure compensator spool up. The flow goes through the bridgepassage, around the control spool, and out to the work port.

The signal oil also flows to the chamber above the compensator. The signal oil on the top ofthe pressure compensator valve works against the forces working below the pressurecompensator. When the forces are in balance, the supply oil is metered through the cross-drilled holes in the pressure compensator to provide work port oil. The pressure of the signaloil is limited by the signal relief valve.

When more than one circuit is activated at the same time, the highest work port pressure isdirected to the signal duplication valve. The signal duplication valve sends the signal oil to thechamber at the top of all pressure compensators valves.

With the same circuit pressure working on all pressure compensators, the pressure differentialacross all shifted control stems is the same, as shown in the illustration for the pressurecompensator for valve "C" and for valve "B." The pressure differential across the control stemswill be the same value whether the pump can supply the flow demand for all activated circuitsor not.

For example, if the margin pressure is 2100 kPa (300 psi) the pressure differential between thepump supply passage and the feeder passage is approximately 2100 kPa (300 psi) regardless ofwhat the circuit pressure is. With multiple valves activated, the individual circuit pressures willvary.

When the pump cannot meet the flow needs of all activated circuits, the pressure compensatorswill move down to proportion the pump flow in relation to the amount of control spool traveland pressure for each circuit. The pressure differential will be less than described in theexample, but the pressure differential will be the same for all spools.

Valve "B" pressure compensator shows what occurs when an additional circuit is activated witha lower circuit pressure than the first activated valve.

The pressure compensator valve will respond to changes in the circuit pressure by opening andclosing off the passage between the feeder passage and the bridged passage to maintain aconstant flow rate for a given control stem displacement. As the compensator opens and closes,the pressure differential across the compensator will vary in order to maintain a constant flowrate to the implement. The pressure differential across the main control spool is the same forall activated main control spools.

SERV7105-09 - 35 - NPIVol. 9, No. 1, 2005

The load signal from the valve "C" pressure compensator is directed to the top of the valve "B"pressure compensator valve with the lower circuit pressure. When the control spool is moved,pressure oil in the feeder passage moves the pressure compensator valve up. The pressurecompensator valve does not move up enough to open the resolver valve to the signal networkdue to the higher forces working on the resolver valve.

The pressure compensator valve will respond to changes in the circuit pressure by opening andclosing off the passage between the feeder passage and the bridged passage to maintain aconstant flow rate for a given control spool displacement. As the compensator opens andcloses, the pressure differential across the compensator will vary in order to maintain a constantflow rate to the implement, while the pressure differential across the main control spool is thesame for all activated main control spools.

SERV7105-09 - 36 - NPIVol. 9, No. 1, 2005

29

Implement Hydraulic System - DUMP

When the tilt control lever is moved into the DUMP position, a load sensing signal pressureequal to work port pressure is directed to the resolver network. The signal oil goes through theresolver to the top of the signal duplication valve. The signal duplication valve shifts down.Pump flow goes through the signal duplication valve to the bottom of the duplication valve andthe orifice. The duplication valve and the orifice stabilizes the load sensing signal pressure tothe pump control, the spring chamber on each compensator valve, and to the pressuredifferential relief valve. The load sensing pressure acting on the bottom of the pressuredifferential relief valve causes the pressure setting to increase. The pilot pressure reducingvalve limits maximum pilot pressure to 3450 ± 170 kPa (500 ± 25 psi). The implement pumpoil flows through the cover manifold and regulated pilot oil is directed to the various implementfunction solenoid valves.

The load sensing signal moves the pump load sensing spool in the pump control valve toupstroke the pump. The signal circuit is also equipped with a choke check valve. The valvewill allow free flow to the pump control valve. Also, the choke check valve will slow thesignal flow return back to the hydraulic tank.

SERV7105-09 - 37 - NPIVol. 9, No. 1, 2005

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With the control lever moved to DUMP direction, current proportional to the movement of thecontrol lever is directed to the coil on the dump pilot solenoid valve. The solenoid valve sendsa proportional amount of pilot oil to the dump end of the tilt stem. The tilt spool begins to shiftupward. The lower end of the tilt spool is active.

Supply oil flowing through the inlet manifold is directed around the lands of the tilt spool to theload check valve. The check valve unseats. Supply oil flows to the tilt pressure compensatorvalve. The oil flow through the compensator valve is blocked. As the pressure at the top of thecompensator valve increases, the oil pressure shifts the compensator spool downward. Thesupply oil flows through the compensator valve and back around the tilt spool to the rod end ofthe tilt cylinder.

The supply oil is directed to rod end of the tilt cylinder. Also, as the tilt lever is moved, thesolenoid for the tilt anti-drift valve is energized. The oil from the head end of the tilt cylinderflows around the load check valve, through the tilt spool, and back to tank.

Oil directed to the rod end of the tilt cylinder through the bridge passage is also directed to thetilt ball resolver in the resolver network. As the work port pressure increases the pressure inthe resolver network, the resolver ball shifts and blocks oil from any other resolvers in thenetwork. The oil at the tilt ball resolver is directed to the top of the signal duplication valve.

The dump operation is also equipped with a makeup and line relief valve. The line relief valveregulates the pressure spikes caused by outside forces acting on the work tool. This allows thepressure spike to return to the hydraulic tank. This will prevent high pressure from damagingany components in the work tool or actuators. The line relief valve acts like a makeup valve,when the pump can not supply the amount of oil needed to fill the void in the cylinder. Whenthe negative pressure occurs in the tilt cylinder, the valves moves off the seat and tank oil flowsaround the valve to fill the void in the cylinder.

NOTE: The pilot line used on the optional Command Control Steering has been removed fromthe illustration.

SERV7105-09 - 38 - NPIVol. 9, No. 1, 2005

30

Implement Hydraulic System - RAISE

When the lift control lever is moved to the RAISE position, the lift lever position sensor sendsa proportional electronic signal to the Implement ECM. The Implement ECM sends acorresponding proportional signal to the raise pilot solenoid valve. The Implement ECM alsosends a fixed signal to the lift anti-drift valve. A proportional amount of pilot oil is directedfrom the raise pilot solenoid valve to the top of the lift spool. The lift spool shifts downward.

Initially, as the lift spool begins to shift, any work port pressure will enter the control valve andis directed around the spool to the feeder passage. The work port oil pressure goes through theholes in the pressure compensator valve to the area between the compensator valve and the loadcheck spool. The oil pressure helps the spring force hold the pressure compensator valve downto function as a load check valve.

As the control spool shifts down, supply oil flows through the throttling slots into the supplypassage. The pressure compensator valve will move up to the load check spool as the pumpdischarge pressure increases above the work port pressure. The pump system oil pressure flowsthrough the orifices in the pressure compensator valve to the feeder passage, around the liftanti-drift valve, and to the head end of the lift cylinder.

SERV7105-09 - 39 - NPIVol. 9, No. 1, 2005

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The pressure at the work port begin to increase which increases the pressure in the lift resolvernetwork. The ball resolver moves downward and oil flows through the resolver network to thetop of the signal duplication valve.

The signal duplication valve shifts and sends a matching resolver network pressure out of theduplication valve over the choke check valve to the pump control valve. The implement pumpupstrokes to supply the flow demand.

Also, matching oil from the signal duplication valve flows to the pressure compensator valveworking on the bottom of the compensator valve. As the pressure changes in the head end ofthe lift cylinders, the pressure compensator valve opens and closes to maintain a constant flowfor a given control spool displacement.

If the machine is equipped with the optional ride control, the balance valve solenoid will beenergized, allowing oil on the right side of the balance valve to go to the hydraulic tank. As thepressure in the head end of the lift cylinders increases to raise, the oil pressure on the left sideof the balance valve will force the balance valve to shift to the right. Supply oil flows over thecheck valve, through the balance valve to the ride control accumulator, charging theaccumulator.

With ride control not enabled, the head end solenoid valve is de-energized and the accumulatorcharge oil will block the flow of oil between the head end of the lift cylinders and theaccumulator.


SERV7105-09 - 40 - NPIVol. 9, No. 1, 2005

31

Implement Hydraulic System - FLOAT

When the lift lever is moved to the FLOAT position, the lift lever position sensor sends aproportional electronic signal to the Implement ECM. The Implement ECM sends acorresponding proportional electronic signal to the lower/float pilot solenoid valve. TheImplement ECM also sends a fixed electronic signal to the lift load check valve.

Pilot oil flows from the lower/float pilot solenoid valve to the bottom of the lift spool and thelift spool shifts up fully. System oil pressure is blocked. Also, oil flow through the pressurecompensator loop is blocked. Oil from the head end and rod end of the lift cylinders along withthe oil to the resolver network is open to tank.

In the FLOAT position, the pilot oil also flows to the resolver valve in the ride control section,through the resolver network to the signal duplication valve. A matching signal (pilot pressure)is directed to the pump control valve from the signal duplication valve. The pump is upstrokedto meet the demand required by the pilot pressure.

SERV7105-09 - 41 - NPIVol. 9, No. 1, 2005

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As the machine moves, the lift cylinders move up and down with the contour of the ground.The check valve allows oil to flow to the lift cylinders when the pressure in the lift cylindersdrops below tank pressure.

SERV7105-09 - 42 - NPIVol. 9, No. 1, 2005

32

Implement Hydraulic System - TILT BACK AND RAISE

When the lift control lever is moved to the RAISE position and the tilt control lever is moved tothe TILT BACK position, the lift lever position sensor and tilt lever position sensor sends anindividual proportional electronic signal to the Implement ECM. The Implement ECM sends acorresponding proportional signal to the raise pilot solenoid valve and the tilt back pilotsolenoid valve. The Implement ECM also sends a fixed signal to the lift and tilt anti-driftvalve. A proportional amount of pilot oil is directed from the raise pilot solenoid valve to thetop of the lift spool and a proportional amount of pilot oil is directed from the tilt back pilotsolenoid valve to the top of the tilt spool. The lift spool shifts downward.

Initially, as the lift spool begins to shift, any work port pressure will enter the control valve andis directed around the spool to the feeder passage. The work port oil pressure goes through theorifices in the pressure compensator valve in between the compensator valve and the load checkspool. The oil pressure helps the spring force hold the pressure compensator valve down.

Identically, as the tilt spool begins to shift, any work port pressure will enter the control valveand is directed around the spool to the feeder passage.

SERV7105-09 - 43 - NPIVol. 9, No. 1, 2005

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The work port oil pressure goes through the holes in the pressure compensator valve to the areabetween the compensator valve and the load check spool. The oil pressure helps the springforce hold the pressure compensator valve down to function as a load check valve.

As the cylinders start to move, the pressure at the work ports increases which increases thepressure in the resolver network. The ball resolver with the highest work port pressure movesseats and blocks oil flow back through the resolver network. The highest work port pressureflows through the resolver network to the top of the signal duplication valve.

The signal duplication valve shifts and sends the matching resolver network pressure out of theduplication valve over the choke check valve to the pump control valve. The implement pumprecognizes a demand for increased oil flow and the pump upstrokes to supply the flow demand.

Also, matching oil from the signal duplication valve flows to the pressure compensator valveworking on the bottom of the load check spool. As the pressure changes in the head end of thelift cylinders, the pressure compensator valve opens and closes to maintain a constant flow fora given control spool displacement.

If the machine is equipped with the optional ride control, the balance valve solenoid will beenergized, allowing oil on the right side of the balance valve to go to the hydraulic tank. As thepressure in the head end of the lift cylinders begins to raise, the oil pressure on the left side ofthe balance valve will force the balance valve to shift to the right. Supply oil flows over thecheck valve, through the balance valve to the ride control accumulator, charging theaccumulator.

With ride control not enabled, the head end solenoid valve is de-energized and the accumulatorcharge oil will block the flow of oil between the head end of the lift cylinders and theaccumulator.


SERV7105-09 - 44 - NPIVol. 9, No. 1, 2005

33

Implement Hydraulic System - RIDE CONTROL AUTO

When the ride control system is in AUTO and the machine reaches the configured ride controlground speed, the ride control balance solenoid valve is de-energized by the Power Train ECM.After the ride control equalization time has expired, the Power Train ECM energizes both theride control head end solenoid valve and the ride control rod end solenoid valve.

The head end solenoid valve connects the head end of the lift cylinders to the ride controlaccumulator. The ride control accumulator dampens the motion of the lift arms which makesthe machine more stable. The rod end solenoid valve allows oil from the tank passage to flowinto the rod ends of the lift cylinders when the lift cylinders move down.

When the machine is in ride control AUTO, the control levers are in the HOLD position, andthe ground speed is more than the 9.7 km/h (6 mph), the control spools are in the HOLDposition blocking all oil flow through the implement control valve to the cylinders. Theresolver network is at tank pressure and the pump is at low pressure standby.

SERV7105-09 - 45 - NPIVol. 9, No. 1, 2005

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When the ground speed reaches the ECM configured value of 9.7 km/h (6 mph), the balancesolenoid valve will be de-energized and the balance spool will move in the direction needed toequalize the pressures on each end of the balance spool.

During the balancing operation, when the pressure at the right side of the balance spool islowest, the spool shifts to the right and the implement pump supplies oil flow to equalize thepressure on both ends of the spool.

During the balancing operation, when the pressure at the left side of the balance spool islowest, the spool shifts to the left and the pressure in the oil pressure in the accumulator flowsto tank until the pressures on both ends of the spool are equal.

The Power Train ECM limits the time to equalize to one second (default). Then, the ECMenergizes the balance solenoid valve. The oil pressure on the right end of the balance spoolflows through the orifice to the hydraulic tank. The balance spool shifts to the right. Oil in theaccumulator is trapped at the check valve.

After the one second balancing time, the rod end solenoid and the head end solenoid valves areenergized. The oil pressure that holds the check valves locked is released to tank. The oil inthe head end of the lift cylinders flows to the ride control accumulator. The accumulatorcushions the forward and backward pitching motions of the machine.

At a ground speed below the ECM configured valve of 9.7 km/h (6 mph), the rod end solenoidand the head end solenoid valves are de-energized. The check valves close and the spring forceand the oil pressure hold the check valves closed.

NOTE: The one second balance default time can be reconfigured in Caterpillar ElectronicTechnician (ET).

SERV7105-09 - 46 - NPIVol. 9, No. 1, 2005

34

Calibrations and Adjustments for Implement Hydraulic System

The implement system calibrations for the "H" Series Medium Wheel Loaders are the same asthey are for the "G" Series II Medium Wheel Loaders. The calibrations should be performed inthe order in which they appear, lever position sensors, linkage position sensors, and theimplement valve calibrations.

The "H" Series Medium Wheel Loaders feature soft detents. When the lever position sensorsare calibrated the levers must be held in the full travel positions.

SERV7105-09 - 47 - NPIVol. 9, No. 1, 2005

35

This screen shot taken from ET shows the ride control configuration line items. The ridecontrol reverse and forward activation speed can be configured. The ride control pressureequalization time can also be configured.

If the operator is complaining about lift arm movement when the ride control engages, twoadjustments can be made. The ride control reverse activation speed can be changed to a verylow value, so that the ride control system engages as the operator backs out of the loading area.The ride control equalization time can be increased to allow more time for the balance valve toequalize the pressure between the head ends of the lift cylinders and the ride controlaccumulator.

SERV7105-09 - 48 - NPIVol. 9, No. 1, 2005

STEERING SYSTEM

The steering systems on the "H" Series Medium Wheel Loaders remain virtually the same. Asmentioned previously, the standard machines are equipped with Hand Metering Unit (HMU)steering. Command Control Steering (CCS) is available as an option. The location of thesteering control valve for both systems has changed. The steering control valve is located onthe output transfer gear (1) of the transmission. This location offers improved access to theadjustable valves on the steering control valve.

This photograph shows the CCS control valve (2), the crossover relief valve (3), the remote tapline for the steering pump output pressure (4), and the pressure reducing valve (5) for thesteering pilot oil.

36

SERV7105-09 - 49 - NPIVol. 9, No. 1, 2005

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FAN AND BRAKE HYDRAULIC SYSTEM

The fan and brake pump (1) is located on the front gear train of the engine, on the right side ofthe machine. The fan and brake pump provides oil flow for the electronic demand fan systemand the brake hydraulic system. The signal pressure tap (2) and the outlet pressure tap (3) arelocated on the fan and brake pump.

Also located on the engine on the right side of the machine is the fan control and brakeaccumulator charging valve (4).

37

SERV7105-09 - 50 - NPIVol. 9, No. 1, 2005

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The following components are located on the fan control and brake accumulator charging valve:

- Signal line to the fan and brake pump (1)

- Fan solenoid valve, an electronic output of the Engine ECM which controls the speedof the cooling fan (2)

- Relief valve, limits the maximum pressure in the brake system (3)

- Cut-in valve, maintains minimum brake accumulator pressure (4)

- Return hose to the hydraulic tank (5)

- Cut-out valve, maintains maximum brake accumulator pressure (6)

- Brake pressure switch, warns the operator when brake accumulator pressure is low (7)

- Inverse shuttle valve, maintains equal charge pressure in both accumulators (8)

- Accumulator ports (9)

- Pump inlet port (10)

- Fan motor outlet port (11)

- Priority valve, blocks flow to the fan motor when the brake accumulators are charging (12)

38

SERV7105-09 - 51 - NPIVol. 9, No. 1, 2005

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When the fan and brake system is in the ACCUMULATORS CUT-IN condition, the brakeaccumulator pressure has dropped to 11720 kPa (1700 psi) and the cut-in valve is shifted to theleft. Oil flows from the fan/brake pump through the cut-in valve to the resolver valve. Theresolver valve allows the higher of two pressures between the signal from the fan solenoidvalve and from the cut-in valve to flow to the flow control spool of the pump control valve. Inthis instance the oil from the cut-in valve is higher in pressure. The flow control spool sendsoil to the actuator to control the displacement of the fan/brake pump. Oil also flows to thepriority valve which shifts the priority valve up and partially blocks the flow of oil to the fanmotor.

Oil also flows past the screen, the check valve, and the orifice to the inverse shuttle valve. Theinverse shuttle valve maintains equal pressure in both brake accumulators. The relief valveprotects the brake system from high pressure.

SERV7105-09 - 52 - NPIVol. 9, No. 1, 2005

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The above illustration shows the fan and brake hydraulic system with the brake accumulators inthe ACCUMULATORS CUT-OUT condition. The brake accumulator pressure has increased to14500 kPa (2100 psi) and the cut-out valve momentarily shifted down, allowing the oil on theright side of the cut-in valve to drain to tank. The cut-in valve shifts to the right and blocks theflow of oil to the pump signal system and drains the signal oil from the resolver valve and thepriority valve. The signal oil from the fan solenoid valve flows to the resolver valve and to theflow control spool on the pump control valve. The fan solenoid valve now controls the positionof the swash plate on the fan/brake valve.

Pump oil flows through the screen and is blocked from entering the brake system by the checkvalve. The priority valve is fully shifted down and directs the majority of the pump flow to thefan motor. The fan motor drives the cooling fan, which cools the machine systems.

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Calibrations and Adjustments for Fan/Brake Hydraulic System

The fan system requires a calibration. The calibration is done using Caterpillar ElectronicTechnician (ET). After selecting the Engine ECM, the Engine Cooling Fan Calibration is foundin the Service drop down menu and under Calibrations.

The technician uses ET to adjust the electrical signal to the fan solenoid valve to obtain aminimum fan speed and a maximum fan speed. After the calibration is complete the EngineECM will control fan speed between the minimum and maximum based on inlet manifoldtemperature, hydraulic oil temperature, and coolant temperature.

The Engine Cooling Fan Calibration should be performed after any component of the fan andbrake hydraulic system is replaced, the Engine ECM is replaced, or the Engine ECM softwareis flashed. If the minimum and maximum speeds can not be obtained during the calibrationthere may be a problem with the fan/brake pump or elsewhere in the system.

SERV7105-09 - 54 - NPIVol. 9, No. 1, 2005

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NEW TOOLING/SKILLS REQUIRED FOR SERVICE

The 966H and 972H Wheel Loaders have many electronically controlled components. A strongknowledge of Caterpillar Electronic Technician (Cat ET) is required for many service activities.

42

SERV7105-09 - 55 - NPIVol. 9, No. 1, 2005

CONCLUSION

This presentation has provided New Product Introduction (NPI) information for the Caterpillar966H and 972H Wheel Loaders. Always use the latest Service Information to ensure that themost current specifications and test procedures are used.

43

SERV7105-09 - 56 - NPIVol. 9, No. 1, 2005

HYDRAULIC SCHEMATIC COLOR CODE

This illustration identifies the meanings of the colors used in the hydraulic schematics and cross-sectional views shown throughout this presentation.

SERV7105-09 - 57 - NPIVol. 9, No. 1, 2005

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SERV7105-09 - 58 - NPIVol. 9, No. 1, 2005

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SERV7105-09 - 59 - NPIVol. 9, No. 1, 2005 Handout No. 1

Machine Orientation Checklist

Directions: Use this sheet when performing the machine orientation lab exercise.

Place a check in the blank if the fluid level is acceptable.

____ Engine oil level____ Hydraulic system oil level____ Autolube lubrication system grease level (if equipped)____ Final drive and differential oil level____ Cooling system fluid level ____ Fuel level

Place a check in the blank if acceptable or after task was performed.

____ Check the Caterpillar Monitoring System for abnormal machine conditions____ Check seat belt____ Check the air filter precleaners

Place a check in the blank if the indicator, switch, or control is working correctly.

____ Key start switch____ Engine coolant temperature gauge____ Fuel level gauge____ Power train oil temperature gauge____ Hydraulic oil temperature gauge____ Ride control indicator light (if equipped)____ Autoshift indicator light____ Front and rear work lights____ Front and rear work lights____ Windshield wipers (if equipped)____ Heating and air conditioner controls (if equipped)____ Back-up alarm


Machine Orientation Checklist - continued

Place a check in the blank after locating and reading the following warnings label on themachine.

____ ROPS____ Parking brake____ No clearance (articulation joint)____ Radiator____ Batteries____ Unit injectors____ Do not operate

Place a check in the blank after locating each of the following controls.

____ Throttle pedal____ Left brake pedal____ Right brake pedal____ Tilt lever____ Lift lever____ Parking brake knob____ Steering Wheel____ Ground level shutdown switch____ Battery disconnect switch

Place a check in the blank after locating each of the following identification plates.

____ Product Identification Number (PIN)____ Engine serial number____ Transmission serial number ____ Bucket serial number


Machine Posttest

Directions: Answer each question with the best possible answer.

1. The 972H Wheel Loader is equipped with which engine?a. 3196b. C13 ACERT™c. C15 ACERT™d. 3176

2. The 966H/972H Wheel Loaders are equipped with combination fan and brake valve.a. Trueb. False

3. The diagnostic lines group is an attachment on 966H/972H Wheel Loader.a. Trueb. False

4. The 966H/972H Wheel Loader are equipped with which style implement hydraulicsystem?a. AMOCSb. LS/PCc. Open centerd. 3PC

5. The 966H/972H Wheel Loaders require service personnel to use Cat ET to calibrate thefan hydraulic system.a. Trueb. False


Machine Posttest - Continued

6. The 966H/972H Wheel Loaders ride control system utilizes: a. Two solenoid valvesb. A balance valvec. Four accumulatorsd. Both a and b

7. The 966H/972H Wheel Loader are equipped with what type Engine ECM?a. ADEM IIIb. A4M1c. ADEM IVd. A4E4

8. The hydraulic tank on the 966H/972H is located:a. On the right side of the machineb. Behind the cabc. On the left side of the machined. On the rear of the machine

9. Where are the remote pressure taps located on the 966H/972H Wheel Loaders?a. On the service center, left side of the machineb. On the service center, right side of the machinec. Behind the cab, in the pump bayd. Next to the battery disconnect switch

10. The 966H/972H Wheel Loaders are equipped with an implement electrohydraulicsystem.a. Trueb. False

11. The 966H Wheel Loader is equipped with which engine?a. 3196b. C11 ACERT™c. C13 ACERT™d. 3176

SERV7105-09 - 63 - NPIVol. 9, No. 1, 2005 Posttest Answers

Machine Posttest Answers

Quiz Answers:

1. b

2. a

3. b

4. d

5. a

6. b

7. d

8. b

9. b

10. a

11. b

curso cat 966h-972h stmg

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