Usage:
793C (4AR),
RM523, 793C (4GZ),
RM596 Off-Highway Trucks
Description of Change: The high steering pressure switch on the 793C Off-Highway Trucks has been relocated to improve service life. The new location, on the bottom of the steering accumulator, reduces the pressure fluctuations that may be harmful to the pressure switch.
Use the following procedure to relocate the steering pressure sensor.
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Sudden release of oil under pressure can cause possible injury or death to persons on or near the machine. Refer to Step 1, A through D for the procedure to relieve steering system pressure.
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1. Relieve all pressure from the steering system by using the following procedure:
A. Push the button for the pressure release on the top of the breaker relief valve. The breaker relief valve is located on the top of the steering tank.
B. Loosen the filler cap on the tank for the steering hydraulic oil.
C. Turn the steering wheel several times in order to remove any residual pressure.
D. Make sure all the hydraulic pressure is released before any component is removed.
Illustration 1.
View removing the existing pressure switch assembly connector.
2. Disconnect the existing wiring connector from the high steering pressure switch.
Illustration 2.
View of the existing "T" to be removed.
3. Remove the existing 3E-6461 Pressure Switch Assembly (C) and O-ring from the fitting (D) that is located on the metering block.
4. Remove the existing "T" fitting (D) that is located on the metering block.
Illustration 3.
View of the elbow assembly installed.
5. Install one 6V-8724 Elbow (1) with one 3J-1907 Seal and one 6V-8397 Seal in the former position of the "T" fitting in the metering block. Tighten the elbow assembly to a torque of 20 N·m ± 2 N·m (15 ± 1.5 lb ft).
Illustration 4.
View of the position of the existing plug.
6. Remove the existing plug from the rear steering accumulator.
Illustration 5.
View of the existing pressure switch and O-ring installed.
7. Install the existing pressure switch with one 3J-7354 O-ring Seal in the rear steering accumulator. Tighten the pressure switch to a torque of 20 N·m ± 2 N·m (15 ± 1.5 lb ft).
8. Separate the existing connector (B) from the harness by cutting the wiring harness 254 mm (10.0 in) back from the connector end. The connector and wires will be reused.
Illustration 6.
Wiring diagram of the extension wiring harness.
9. Use one 102-8802 Receptacle Assembly (2) and two 8T-8729 Connector Pins (4) in order to terminate the two wires on the existing frame wiring harness (A).
A. Attach the two 8T-8729 Connector Pins (4) to the two existing wires on the frame wiring harness.
B. Insert the wire number F447-PU into location 1 of the receptacle assembly.
C. Insert wire number J765-BU into location 2 of the receptacle assembly.
10. Use one 155-2270 Connector Plug Kit (3) and two 8T-8730 Socket Connectors (5) in order to terminate the wires on the existing wires to the existing pressure switch assembly (B).
A. Attach the wire to the two 8T-8730 Socket Connectors (5) to the existing wires on the existing pressure switch assembly (B).
B. Insert wire number F447-PU into location 1 of the connector plug.
C. Insert wire number J765-BU into location 2 of the connector plug.
11. Use two 750 mm (42.0 in) lengths of 16 gauge wire (7), one 102-8802 Receptacle Assembly (2), two 8T-8729 Connector Pins (4), one 155-2270 Connector Plug Kit (3), and two 8T-8730 Socket Connectors (5) in order to make an extension wiring harness.
A. Protect the pair of wires of the extension wiring harness by installing an appropriate length of 9X-1813 Sleeve (12) over the wires.
B. Install two 8T-8729 Connector Pins (4) to one end of the pair of wires (7) and insert the wires into the 102-8802 Receptacle Assembly (2).
C. Install two 8T-8730 Socket Connectors (5) on the other end of the pair of wires (7). Insert the socket connectors into the 155-2270 Connector Plug Kit (3).
NOTE: Insert the wires into the connectors ensuring that pin 1 goes to pin 1 and pin 2 goes to pin 2.
Illustration 7.
View of the approximate location of the weld bosses.
12. Weld two 7X-7962 Weld Bosses (6) on the frame in the approximate area as shown in the illustration.
13. Connect the pressure switch assembly connector (MS plug) to the existing pressure sensor and secure the connector with a safety wire.
14. Connect the extension wiring harness (fabricated in Step 11) to the pressure switch wiring harness termination plug.
15. Connect the new extension harness to the existing frame wiring harness.
Illustration 8.
16. Use two 5P-9297 Clips (8), two 8T-4121 Washers (9), and two 8T-4136 Bolts (10) to secure the harness to the two 7X-7962 Weld Bosses (6). Secure the harness with wire ties as necessary.
17. Check for proper fluid levels. Test for leaks and proper operation.
Effective With: The relocation of the high steering pressure switch is effective with 793C (4GZ148).
Adaptable To: The relocation of the high steering pressure switch is adaptable to 793C (4GZ1-147) and 793C (4AR1-Up).