It is one of the switches used in the upper consoles. The two speed function is activated by depressing the two speed switch. This process allows the motor to spin faster. The two speed function activates a solenoid valve which blocks the flow of hydrostatic oil to half of the pistons in the drive motors. The auxiliary hydraulic ECM controls the two speed function. The two speed function is an optional attachment on certain models. On high flow machines with the mode switch in auxiliary hydraulic mode, the control flow solenoid will energize. On machines with XPS high flow, the control flow solenoid will be disabled reducing system pressure. Pressing the C- switch on the right joystick in order to provide hydraulic oil flow to the hydraulic connector on the loader arm. Pressing the C+ switch on the right joystick in order to provide hydraulic oil flow to the hydraulic connector on the loader arm. The secondary auxiliary (hydraulic flow) utilizes another set of lines that run down the lift arm for worktool positioning. The secondary auxiliary is only available on machines equipped with either high flow option. When the proportional control is moved to the A2 position, the auxiliary A2 solenoid will only energize. When the proportional control is moved to the A1 position, the auxiliary solenoid A2 and the high flow solenoid will energize. When the mode switch is in the high flow position, the ECM will energize the control flow solenoid. The high flow option is available on some machines. When the proportional control is moved to the A2 position, the auxiliary solenoid A2 and the control flow solenoid will energize. When the proportional control is moved to the A1 position and the mode select switch is in the high flow mode, the auxiliary solenoid A1 and the control flow solenoid will energize. The system uses a proportional control on the work tool lever. The XPS high flow function is available on the High Flow models only. Note: Raising the armrest and/or exiting the seat without enabling the interlock override function will reset the ECM. When the continuous flow function is enabled, depress the interlock override switch in order to enable the interlock override function. The interlock override function will allow the operator to raise the armrest in order to exit the machine while the A1 solenoid or the A2 solenoid remains energized. The A1 switch or A2 switch must be released within one second of pressing the continuous flow switch. Once either the A1 solenoid or the A2 solenoid is energized, pressing the continuous flow switch and releasing the A1 switch or A2 switch will allow the solenoid to remain energized. The continuous flow function allows the flow of hydraulic oil to the auxiliary hydraulics without the need of continuously actuating the auxiliary control. Moving the auxiliary control backward will energize the A2 solenoid for the auxiliary hydraulics. Moving the auxiliary control forward will energize the A1 solenoid for the auxiliary hydraulics.

High current loads often cause the failures we have seen.

Cat 277b service manual