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784C, 785C and 785C HAA Off-Highway Truck Air System and Brakes Caterpillar


Air System

Usage:

785C 1HW
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Illustration 1g01061531
(1) Autolube reservoir
(2) Air tank check valves
(3) Drain valves
(4) Primary air tank
(5) Starter relay valve
(6) Attachment shutters for the left cylinder and for the right cylinder
(7) Attachment inversion valve
(8) Solenoid valve for attachment shutters
(9) Air relief valve for primary air tank
(10) Starter solenoid valve
(11) Air starting motor
(12) Brake air relay valve
(13) Pressure protection valve for the brake air system
(14) Brake air relay valve for the Automatic Retarder Control (ARC)
(15) Air compressor with air compressor governor
(16) Air dryers with air relief valve
(17) Double check valves
(18) Parking and secondary brake valve
(19) Torque converter and front brake cooling diverter valve
(20) Brake master cylinder (front)
(21) Brake master cylinders (rear)
(22) External air supply
(23) Air suspension seat
(24) Solenoid valve for autolube
(25) Air system pressure protection valve
(26) Air suspension buddy seat that is an attachment
(27) Cleanout hose that is an attachment
(28) Air horn solenoid
(29) Service brake air control valve
(30) Automatic Retarder Control (ARC) valve
(31) Retarder air control valve
(32) Secondary brake air control valve
(33) Parking brake (air control valve)
(34) Secondary air tank
(35) Air horn
(36) Secondary brake inverter valve
(37) Parking brake valve (reset)
(38) Cab wall
(A) This is the brake air pressure sensor. The brake air pressure sensor monitors brake air pressure. The operator will be alerted to a condition of low air pressure.
(B) This is the secondary brake and parking brake pressure switch. This pressure switch is normally open. The pressure switch is closed by air pressure when the parking brakes or secondary brakes are released. When this pressure switch is open, this pressure switch signals the Power Train Electronic Control Module (Power Train ECM) to allow rapid shifts.
(C) This is the brake cylinder overstroke limit switch (overstroke switch). The overstroke switch is normally closed. The overstroke switch opens when the pistons in the master cylinder travel too far. A brake overstroke condition can result from low brake fluid level, air in the brake hydraulic circuit, leakage in the brake hydraulic lines, and master cylinder piston seal leaks. An indicator will come on in the cab and the alarm will sound. Do not operate the machine until the cause for the overstroke has been corrected.
(D) This is the pressure switch for the service brake and the retarder. This pressure switch is normally closed. This pressure switch is opened by air pressure when the service brakes, the retarder, or the Automatic Retarder Control (ARC) are applied. When this pressure switch is open, the pressure switch signals the Power Train ECM in order to allow the transmission to perform rapid shifts. The Power Train ECM also indicates that higher engine rpm is needed for upshifts or for downshifts of the transmission when this pressure switch is open.
(E) This is the stop lights pressure switch. This pressure switch is normally open. This pressure switch is closed by air pressure when the service brakes, the retarder, or the Automatic Retarder Control (ARC) are applied. When this pressure switch is closed, this pressure switch activates the stop lights.
(F) This is the Automatic Retarder Control pressure switch. This pressure switch is normally closed. This pressure switch is opened by air pressure in order to indicate that the Automatic Retarder Control (ARC) is operating. The pressure switch verifies that air pressure is being provided through the Automatic Retarder Control valve.
(G) This is the manual retarder pressure switch. This pressure switch is normally open. This pressure switch is closed when the retarder air control valve is applied. This switch operates the indicator in the cab.

Location Of Components

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Illustration 2g00903434
Compartment in the front of the cab
(17) Double check valve
(29) Service brake air control valve
(30) Automatic Retarder Control valve
(32) Secondary brake air control valve
(F) Automatic Retarder Control pressure switch
(G) Manual retarder pressure switch
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Illustration 3g00903437
(31) Retarder air control valve
(33) Parking brake (air control valve)
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Illustration 4g00915084
(33) Parking brake (air control valve)
(37) Parking brake valve (reset)
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Illustration 5g00908215
Compartment in the rear of the cab
(2) Air tank check valve
(34) Secondary air tank
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Illustration 6g00903442
Compartment in the rear of the cab
(36) Secondary brake inverter valve
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Illustration 7g00903444
Compartment in the rear of the cab
(25) Air system pressure protection valve
(A) Brake air pressure sensor
(B) Secondary brake and parking brake pressure switch
(D) Service brake and retarder pressure switch
(E) Stop lights pressure switch
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Illustration 8g00903447
Top view of air lines for the chassis
(4) Primary air tank
(12) Brake air relay valve
(13) Pressure protection valve for the brake air system
(14) Brake air relay valve for the Automatic Retarder Control (ARC)
(15) Air compressor with an air compressor governor
(16) Air dryers with an air relief valve
(18) Parking and secondary brake valve
(19) Torque converter and front brake cooling diverter valve
(20) Brake master cylinder (front)
(21) Brake master cylinders (rear)
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Illustration 9g00903448
Side view of air lines for the chassis
(2) Air tank check valve
(4) Primary air tank
(12) Brake air relay valve
(13) Pressure protection valve for the brake air system
(14) Brake air relay valve for the Automatic Retarder Control (ARC)
(15) Air compressor with an air compressor governor
(16) Air dryer with an air dryer relief valve
(18) Parking and secondary brake valve
(19) Torque converter and front brake cooling diverter valve
(20) Brake master cylinder (front)
(21) Brake master cylinders (rear)

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