CAGE 8Y0785 - Caterpillar

Introduction
This Special Instruction provides the information that is needed in order to bypass the auxiliary hydraulic controller which will then allow the switches on the left hand joystick to directly control the medium pressure circuit when the auxiliary hydraulic circuit is switched in the one-way mode.The current configuration of the auxiliary hydraulic circuit that is in the 300B series of hydraulic excavators does not allow the medium pressure circuit to be used when the auxiliary hydraulic circuit is switched in the one-way mode. One of the switches on the left hand joystick that is used to activate the medium pressure circuit is reserved for the second speed of the hydraulic hammer when the auxiliary hydraulic circuit is switched in the one-way mode.Do not perform any rework procedures until you have read the information in this publication.Refer to the appropriate Parts Manual for the location of the hardware.Note: As a result of modifying the circuit, the second speed of the hydraulic hammer will be disabled when the auxiliary hydraulic circuit is switched in the one-way mode. The switches on the left hand joystick will now be used for the medium pressure circuit. The circuit modification will also allow higher current to flow through the switches. Over a period of time, the sensitivity of the switches to lower currents will be reduced. It will then be difficult to return to applications that require lower currents. After modifying the circuit, the 134-5298 Film inside the cab must be replaced by the 179-0898 Film .Procedure For The Wiring Modification
Illustration 1 g00654819
Schematic of the Modified Auxiliary Hydraulic CircuitThe auxiliary hydraulic controller is bypassed in order to allow the switches on the left hand joystick to directly control the medium pressure circuit. This is accomplished by performing the following steps.
Disconnect the second speed solenoid of the hydraulic hammer "HAMMER 2 SOL ON/OFF" from the auxiliary controller by disconnecting the pink wire "951" from the controller.
Disconnect the switches of the left hand joystick and the medium pressure solenoid "MEDIUM PRESSURE SOL R1/R2" from the auxiliary controller.
For the switches of the joystick, disconnect the orange wire "547" and the blue wire "546" from the controller.
For the medium pressure solenoid, disconnect the pink wire "A848" and the yellow wire "A847" from the controller.
Connect the orange wire "547" to the yellow wire "A847".
Connect the blue wire "546" to the pink wire "A848".