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


Air System

Usage:

784C 2PZ
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Illustration 1g00902956
(1) Auto lube tank
(2) Air tank check valves
(3) Drain valves
(4) Primary air tank
(5) Air relief valve for primary air tank
(6) Brake air relay valve for the pulled unit
(7) Attachment shutters for the left cylinder and for the right cylinder
(8) Attachment inversion valve
(9) Solenoid valve for attachment shutters
(10) Starter solenoid valve
(11) Starter relay valve
(12) Air starting motor
(13) Brake master cylinders (pulled unit)
(14) Air compressor with air compressor governor
(15) Air dryers with air relief valve
(16) Brake air relay valve
(17) Brake air relay valve for the Automatic Retarder Control (ARC)
(18) Pressure protection valve for the brake air system
(19) External air supply
(20) Torque converter and front brake cooling diverter valve
(21) Air suspension seat
(22) Solenoid valve for AUTO lube
(23) Pulled unit air control valve
(24) Air suspension buddy seat that is an attachment
(25) Cleanout hose that is an attachment
(26) Air horn solenoid
(27) Air system pressure protection valve
(28) Parking and secondary brake valve
(29) Automatic Retarder Control (ARC) valve
(30) Double check valves
(31) Service brake air control valve
(32) Brake master cylinder (front)
(33) Brake master cylinders (rear)
(34) Air horn
(35) Retarder air control valve
(36) Parking brake (air control valve)
(37) Secondary brake inverter valve
(38) Parking brake (reset valve)
(39) Secondary air tank
(40) Secondary brake air control valve
(41) 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 switches. This pressure switch is normally open. This pressure switch is closed by air pressure when the service brakes, the retarder, the Automatic Retarder Control (ARC), or the pulled unit air control valve 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 2g00903185
Compartment in the front of the cab
(29) Automatic Retarder Control valve
(30) Double check valve
(31) Service brake air control valve
(40) Secondary brake air control valve
(F) Automatic Retarder Control pressure switch
(G) Manual retarder pressure switch
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Illustration 3g00914972
(36) Parking brake (air control valve)
(38) Parking brake (reset valve)
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Illustration 4g00903187
(23) Pulled unit air control valve
(35) Retarder air control valve
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Illustration 5g00903188
Compartment in the rear of the cab
(2) Air tank check valve
(37) Secondary brake inverter valve
(39) Secondary air tank
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Illustration 6g00903191
Compartment in the rear of the cab
(27) 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 7g00903195
Top view of air lines for the chassis
(4) Primary air tank
(6) Brake air relay valve for the pulled unit
(16) Brake air relay valve
(13) Brake master cylinders (pulled unit)
(14) Air compressor with an air compressor governor
(15) Air dryers with an air relief valve
(17) Brake air relay valve that is for the Automatic Retarder Control
(18) Pressure protection valve for the brake air system
(20) Torque converter and front brake cooling diverter valve
(28) Parking and secondary brake valve
(32) Brake master cylinder (front)
(33) Brake master cylinders (rear)
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Illustration 8g00903197
Side view of air lines for the chassis
(2) Air tank check valve
(4) Primary air tank
(6) Brake air relay valve for the pulled unit
(13) Brake master cylinders (pulled unit)
(14) Air compressor with an air compressor governor
(15) Air dryers with an air relief valve
(16) Brake air relay valve
(17) Brake air relay valve for the Automatic Retarder Control
(18) Pressure protection valve for the brake air system
(20) Torque converter and front brake cooling diverter valve
(28) Parking and secondary brake valve
(32) Brake master cylinder (front)
(33) Brake master cylinders (rear)

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