SUPPORT 2109001 - Caterpillar

Illustration 6 g00932058
Pilot lines at the main control valve (top view)
When joystick (25) and/or joystick (26) are operated, the pilot control valves send pilot pump oil through the pilot lines to pilot ports at the main control valve to shift the spools in the main control valve. Refer to Illustration 6 and Table 1 for the location of the pilot lines and machine operations.
Table 1
Pilot line Control Valve Machine Operation
(76) Boom l control valve BOOM LOWER
(77) Bucket control valve BUCKET CLOSE
(78) Swing control valve SWING LEFT
(79) Boom II control valve BOOM RAISE
(80) Stick II control valve STICK IN
(81) Right travel control valve REVERSE RIGHT TRAVEL
(82) Left travel control valve REVERSE LEFT TRAVEL
(83) Stick l control valve STICK IN Pilot oil from the pilot control valves flows through pilot lines to the ports on the bottom of the main control valve in order to perform the opposite operation.The following example is given for the BOOM LOWER operation and the BOOM RAISE operation. Machine operations for a stick operation, bucket operation, travel operation, and swing operation are accomplished in the same manner as the boom operation.When the joystick for the boom is moved to the BOOM RAISE position, pilot oil from pilot control valve (26) flows through pilot line (37) to boom l control valve (17). The pilot pressure shifts the boom l control valve. The oil delivery from the drive pump flows to the head end of the boom cylinders in order to perform the BOOM RAISE operation.When the joystick for the boom is moved to the BOOM LOWER position, pilot oil from pilot control valve (26) flows through pilot line (6) to boom l control valve (17). The pilot pressure shifts the boom l control valve. The pilot oil also flows through pilot line (7) in order to open boom drift reduction valve (12). The return oil from the head end of the boom cylinders flows through the boom drift reduction valve and the boom l control valve to the hydraulic tank. The BOOM LOWER operation is now performed.Pressure Switch Circuits
Pressure switches (19) and (21) are connected to travel pilot control valve (5). Pressure switch (40) is connected to pilot control valve (25) and pilot control valve (26). When all of the joysticks and/or travel levers/pedals are in the NEUTRAL position, the pilot oil pressure to the pressure switches is low. Pressure switches (19), (21), and (40) are OFF. The machine ECM recognizes the OFF condition of all of the pressure switches. The AEC system is activated in order to lower the engine rpm.If any of the joysticks and/or travel levers/pedals are moved from the NEUTRAL position, the increased pilot oil pressure is sent to the pressure switches. If pressure switch (19), (21), and/or (40) is ON, the machine ECM activates the AEC system in order to increase the engine rpm.If both travel levers/pedals and either one of the joysticks are moved from the NEUTRAL position simultaneously, pilot oil pressure will cause pressure switches (19), (21), and (40) to