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


Air System

Usage:

785C 5AZ


Illustration 1g01056967
(1) Autolube reservoir
(2) Air tank check valves
(3) Primary air tank
(4) Drain valves
(5) Air relief valve for primary air tank
(6) Starter relay valve
(7) Air starting motor
(8) Air compressor with air compressor governor
(9) External air supply
(10) Air dryer with air relief valve
(11) Starter solenoid valve
(12) Torque converter and front brake cooling diverter valve
(13) Brake air relay valve
(14) Cooling diverter solenoid
(15) Brake air pressure sensor
(16) Air suspension buddy seat that is an attachment
(17) Cleanout hose that is an attachment
(18) Air suspension seat
(19) Air horn solenoid
(20) Solenoid valve for autolube
(21) Air system pressure protection valve
(22) Service brake and retarder pressure switch
(23) Secondary brake and parking brake pressure switch
(24) Parking and secondary brake valve
(25) Brake master cylinder (front)
(26) Brake master cylinders (rear)
(27) Air horn
(28) Manual retarder pressure switch
(29) Double check valve
(30) Retarder air control valve
(31) Service brake air control valve
(32) Secondary brake air control valve
(33) Parking brake (air control valve)
(34) Parking brake valve (reset)
(35) Secondary brake inverter valve
(36) Secondary air tank
(37) Cab wall

Brake air pressure sensor (15) monitors brake air pressure. The operator will be alerted to a condition of low air pressure.

Air pressure switch (22) for the service brake and the retarder is normally closed. This pressure switch is opened by air pressure when the service brakes or the retarder are applied. When air pressure switch (22) for the service brake and the retarder 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.

Secondary brake and parking brake pressure switch (23) is normally open. The pressure switch is closed by air pressure when the parking brakes or secondary brakes are released. When secondary brake and parking brake pressure switch (23) is open, this pressure switch signals the Power Train Electronic Control Module (Power Train ECM) to allow rapid shifts.

Manual retarder pressure switch (28) is normally open. This pressure switch is closed when retarder air control valve (30) is applied. Manual retarder pressure switch (28) operates the indicator in the cab.

Location Of Components



Illustration 2g01060116
(29) Double check valve
(31) Service brake air control valve
(32) Secondary brake air control valve


Illustration 3g01057097
(30) Retarder air control valve
(33) Parking brake (air control valve)


Illustration 4g01057166
(33) Parking brake (air control valve)
(34) Parking brake valve (reset)


Illustration 5g01057168
Compartment in the rear of the cab
(2) Air tank check valve
(36) Secondary air tank


Illustration 6g01057172
Compartment in the rear of the cab
(35) Secondary brake inverter valve


Illustration 7g01060419
Compartment in the rear of the cab
(14) Cooling diverter solenoid
(15) Brake air pressure sensor
(21) Air system pressure protection valve
(22) Service brake and retarder pressure switch
(23) Secondary brake and parking brake pressure switch


Illustration 8g01052891
Front view of air lines for the chassis
(3) Primary air tank
(8) Air compressor with an air compressor governor
(10) Air dryer with an air relief valve
(12) Torque converter and front brake cooling diverter valve
(13) Brake air relay valve

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