769D Off-Highway Truck: Pressure Switch (Secondary Steering)

(1) Pressure switch for the secondary steering system

Since The electric drive pump is used to drive the secondary steering, the brake release, the prelubrication, and the high speed oil change (quickevac) a means is needed in order to ensure that the wheels of the machine are not attempting to be turned when the service mode is active. As a result, secondary steering pressure switch (1) that monitors the pressure in the secondary steering circuit will change states if the pressure exceeds a certain level. This would indicate that the wheels are attempting to be turned. When this secondary steering pressure switch (1) changes states during a quickevac, the service indicator lamp will continually flash indicating a system error. Also, the ECM will turn off the relay and the ECM will not allow the relay to be turned on again until the service switch is cycled. This cycling of the switch must be done while the key switch is in the OFF position. At this point, a quickevac is allowed via the 187-1458 High Speed Oil Change Tool Gp .

The quickevac error mode is enabled anytime, when secondary steering pressure switch (1) is ON and while the Engine Lockout Function is ON. This error indicates that a pressure spike had occurred due to the wheels that are attempting to be turned via the steering wheel. When the quickevac error is enabled the pump will turn OFF and the machine will be inhibited. If the pump was off the pump will stay off. The pump is not allowed to be turned on and the machine will be inhibited until the power is cycled at the service switch. Cycle the service switch while the keyswitch is in the OFF position. The lamp will be ON in this mode.

The quickevac pump will turn OFF, if the pump was ON. Also, the service indicator lamp will flash, if the pump is turned ON. Also, the Engine Lockout Function is enabled while the secondary steering pressure switch (1) indicates that the wheels are being turned. The pump will be OFF and the service indicator lamp will continue to flash until the service switch is cycled.

Note: Remember that the key switch must be in the OFF position when the service switch is cycled.

These safeguards are in place in order to drive a intentional action by the technician. The technician must correct the problem when the wheels are attempting to be turned and a quickevac is trying to be performed. The service indicator lamp will be flashing.

Pressure Switches

(1) Low oil pressure switch for the steering pump

One pressure switch monitors the condition of the steering system.

Oil pressure switch (1) monitors the output of the steering piston pump. Oil pressure switch (1) is attached to the steering check and relief valve that is located on the frame behind the right front suspension cylinder.

The Caterpillar Monitoring System is designed to alert the operator of an immediate problem in the steering system or in other machine systems. The monitoring system also alerts the operator about an impending problem in the steering system or other machine systems.

The oil pressure switch is connected to the monitoring system. The alarm will sound and the action light and alert indicator for the secondary steering system will flash until the steering pressure reaches the deactuation pressure. If the system pressure drops to the actuation pressure, the alarm should sound and the action light should flash.

The oil pressure switch (1) is also connected to the Power Train Electronic Control Module (Power Train ECM). If the system pressure is below the deactuation pressure, the Power Train ECM will energize the secondary steering relay that is located behind the cab. The secondary steering relay behind the cab will then energize a second larger relay that is located on the frame near the front left suspension cylinder. The larger relay will activate the brake release and secondary steering pump. The brake release and secondary steering pump will send oil to the steering check and relief valve.

If the alarm sounds and the alert indicator is flashing, this is an indication of a loss of primary steering flow. The brake release and secondary steering pump will provide enough flow in order to allow the operator to steer the machine to a safe location off the road.

Note: A warning is displayed only if the ground speed is above 8 km/h (5 mph).

MARYGAR

769D Off-Highway Truck: Pressure Switch (Secondary Steering) 2012-11-30T18:49:00-08:00 Rating: 4.5 Diposkan Oleh: Unknown