120H, 12H, 135H, 140H, 143H, 14H, 160H, 163H and 16H Motor Graders Secondary Steering System Hydraulic System Caterpillar

If no electrical problems were found in the Testing and Adjusting, "Electrical System Troubleshooting" section, proceed with the following tests.

Illustration 1	g00927062
(1) Steering cylinders (2) Steering metering unit (3) Hydraulic tank and filter (4) Implement and steering pump (5) Check valve (6) Check valve (7) Combination valve (8) Relief valve (9) Check valve (10) Pump (11) Electric Drive

Illustration 2	g00922990
(12) Secondary steering test switch

Illustration 3	g00922724
Rear compartment on left side of machine (13) Battery disconnect switch

Illustration 4	g00922535
Instrument Panel (14) Action light (15) Panel for the indicator lights (16) Warning light (17) Monitoring panel

General Test Procedures

1. Turn battery disconnect switch (13) to the ON position.

2. Turn the engine start switch to the ON position.

   Note: The secondary steering system will not function unless both of these switches are in the ON position.

3. Warning light (16) and action light (14) should flash until the engine is started. Warning light (16) should stay on for three seconds and electric drive (11) should run for three seconds.

   Note: This three second period is referred to as the three second powerup test.

4. When warning light (16) is on, the operator should be able to steer with a normal amount of effort.

5. Start the engine. After the engine is started, warning light (16) turns off and action light (14) turns off.

6. Turn off the engine. Turn the engine start switch to the ON position. Warning light (16) should flash and action light (14) should also flash. Hold the secondary steering test switch (12) in the TEST position. Electric drive (11) should run. The status light in secondary steering test switch (12) should turn on. The operator should be able to steer with a normal amount of effort.

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NOTICE
The seconday steering motor should remain on for no more than two minutes. This time period should be sufficient to safely steer the machine to a stop. After the machine has come to a stop, turn the engine start switch to the OFF position. This will turn off the secondary steering system. Prolonged use of the secondary steering system will cause the secondary steering motor to overheat. Overheating will cause damage to the components of the secondary steering motor.

7. With the engine at low idle, perform the following steps:
   • Depress the transmission modulator pedal.

   • Depress the brake pedal.

   • Put the transmission direction and speed control in the highest gear.

   • Release the transmission modulator pedal.

   This procedure will stall the engine. After the engine has stalled the following conditions will occur:

   • Warning light (16) flashes.

   • Action light (14) flashes.

   • Electric drive (11) starts running.

   The operator should be able to steer the machine with a normal amount of effort.

The following steps should be used to troubleshoot any problems.

Problem

The operator is unable to steer the machine with a normal amount of effort and the following conditions occur:

• The engine start switch is in the ON position.

• Secondary steering test switch (12) is held in the TEST position.

• Electric drive (11) runs.

• Pump (10) operates.

Probable Cause

• Check valve (9) is sticking.

Check valve (9) is installed on the combination valve. Check valve (9) should unseat when pump (10) is pumping hydraulic oil. The sticking of check valve (9) inhibits the flow of the hydraulic oil from pump (10) to steering metering unit (2) .

Replace check valve (9) .

Problem

The primary steering system does not function. The secondary steering system functions properly.

Probable Cause

• Check valve (6) has failed open. Check valve (6) is mounted in combination valve (7) .

Replace check valve (6) .

Problem

The effort to steer the primary steering system and the effort to steer the secondary steering system is significantly different.

Probable Cause

• Relief valve (8) has failed.

Perform the steps in the Testing and Adjusting, "Relief Valve (Secondary Steering) - Test" section.