Usage:
320B L (7JR, 9WS);
320B LN (3YZ);
320B N (2AS);
322B L (2ES).;
322B LN (1ZS);
325B L (6DN, 4DS, 5BS);
325B LN (8FN);
330B L (3YR, 4RS, 5LS);
330B LN (5LR;
345B L (7KS, 2SW) EXCAVATORS
Problem:
When the auxiliary backup switch is placed in the manual/backup position, the auxiliary controller is disabled. When the auxiliary controller is disconnected, the entire auxiliary system should be disabled. With the current configuration of components, the auxiliary control pedal (1) is still active.
Illustration 1.
In the current configuration, if the auxiliary controller is disconnected and the 4th pedal is pressed, full hydraulic flow will enter the auxiliary implement tool circuit. The full hydraulic flow will cause extreme damage to the tool. The backup switch only disables the auxiliary controller and the auxiliary implement switches on the implement control levers (joysticks). The backup switch still leaves the auxiliary control pedal active and capable of allowing full hydraulic flow into the tool circuit.
Solution:
To correct the problem, the 121-6303 Solenoid Valve needs to be installed on the pilot line to the auxiliary control pedal. The solenoid valve must be plugged into the harness connector (D) provided under the platform, between the harness connection for the lower wiper motor (B) and connection for the attachment auxiliary circuit (C) shown in Illustration 2.
Location under the platform for the connection for the 121-6303 Solenoid Valve Group. 
Illustration 2.
The solenoid valve itself must be connected to the supply pilot line, the pedal pilot line and the drain, as shown in Illustration 3. The correctly installed 121-6303 Solenoid Valve Group will shut off the pilot flow to the auxiliary control pedal (4th pedal) when the auxiliary backup switch is in the manual/backup position.
Hydraulic schematic for installation of 121-6303 Solenoid Valve (4).
Illustration 3.
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