SFN-20240119A Add seat belt alarm circuit

TICO Document #: SFN-20240119A (formerly TES 134)

Description of Procedure: Design revision to seat belt alarm harness to incorporate an additional circuit to prevent starter engagement until operator has fastened seat belt. This circuit is an addition to the alarm circuit in which the horn will blow if the seat belt is not fastened when the park brake is disengaged.

Units Affected: N/A

Parts Required: Relay 90870 (QTY 1)

Terminal, Quick Disconnect, 1/4”, 14-16 gauge (QTY 3)

Terminal, Quick Disconnect, 1/4”, 12 gauge (QTY 2)

Butt Splice, 14-16 gauge (QTY 3)

Butt Splice, 12 gauge (QTY 2)

12 gauge wire, red, GXL (2 ft. required) 16 gauge wire, white, GXL ( 1 ft. required)

16 gauge wire, yellow, GXL ( 1 ft. required)

Planned Labor: 1 hour

Instructions:

1. Park vehicle on flat surface, apply parking brake, and chock wheels. If your company utilizes a “Lock Out, Tag Out” policy, you should employ it during this procedure.

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2. Remove battery box cover and disconnect battery cables. Remove batteries or insulate terminals ends with a non-conductive wrap to prevent inadvertent contact between battery terminals and cables.

3. Release/vent all air in the system. This can be done by manually releasing valves at the bottom of the air tank.

4. Loosen turn signal switch from steering column using flat head screwdriver or 5/16 bit driver.

5. Remove diagnostic panel by removing #10 socket head screws with 1/8” hex key wrench. Panel is located at lower left hand side of dash cover. There are 6 screws for this panel.

6. Behind diagnostic panel, disconnect the connectors for the engine diagnostic switch and the increment/decrement switch.

7. Push connector back into the dash bucket and return diagnostic panel to its original position. Note: Do not secure panel in place at this time.

8. Remove key switch panel from dash cover assembly by removing four #10 socket head screws with 1/8” hex key wrench.

9. Gently pull key switch panel away from dash cover. Remove connector for A/C switch and push it back into dash bucket.

10. Return key switch panel to original position.

    Note: Do not secure panel in place at this time.

11. Gently pull gauge panel away from dash cover.

12. On top right hand side of gauge panel, remove connector for flood lights/work lights switch.

13. Remove air line for air pressure gauge.

14. Continue lifting gauge panel away from dash cover assembly. Locate connector between dash gauge harness and cab PDC harness, shown above.

15. Unscrew connectors securement hardware using 5/16 bit driver.

16. Remove leads to the hour meter, shown on left. Note: red wire on terminal 1, white wire on terminal 2, and brown wire on terminal 3.

17. Remove dash gauge panel with attached harness from dash cover and bucket assembly, set this aside for now.

18. With dash gauge panel and harness removed, locate and identify components of the seat belt alert harness currently installed.

19. Wires that are loomed will need to be exposed so that they can be manipulated easily.

20. Cut the blue wire which connects the seat belt switch to the pressure switch. This connection should be severed inside the dash bucket.

21. Cut orange wire leading from relay to horn wire splice.

22. Butt connect the orange lead from the relay to the blue lead to the pressure switch.

23. Cut white wire that connects timer to ground.

24. Butt splice white lead from timer to orange lead from horn splice.

25. Mount a second relay, Start Inhibit relay, to control the starter circuit.

26. Install a yellow jumper wire from terminal 87a of the Alert relay to terminal 86 of the Start Inhibit relay.

27. Connect a 12 gauge lead to terminal 30 of the Start Inhibit relay.

28. Connect a 12 gauge lead to terminal 87 of the Start Inhibit relay.

29. Connect a white wire lead to terminal 85 of Start Inhibit relay.

30. Locate the K2 relay, neutral start relay, on the power relay block. Remove mounting hardware securing power relay block to plywood backing.

31. Locate the yellow wire coming from the 87 terminal of the K2 relay. This will be labeled as “Start”.

32. Sever the “Start” wire at 5”-6” from the relay block.

33. Splice the 12 gauge wire from terminal 30 on the Start Inhibit relay to the yellow lead, “Start”, from the neutral start relay.

34. Splice the 12 gauge wire from terminal 87 on the Start Inhibit relay to the remaining lead of the “Start” wire.

35. Splice the blue wire from the seat belt switch and the white lead from the Start Inhibit relay to the ground lead wire, formerly timer to ground wire.

36. Inspect work to ensure all splices are insulated properly and all connections are made correctly.

37. Reinstall power relay block.

38. Reinstall dash gauge panel and harness in the reverse order that it was removed in. Ensure no wires are pinched or removed from terminals during this process.

39. Reconnect battery cables to appropriate battery terminals.

40. Test the circuit. With seat harness unbuckled, attempt to start the engine. If this fails proceed to buckle the harness and attempt to start. The starter circuit should engage normally. Apply pressure to the brake pedal and release the park brake, horn alarm should not activate. With park brake released unbuckle the harness, the horn alarm should sound in five seconds. If horn alarm fails to sound or if the unit fails to start, inspect the circuit for missed connections or shorts and repeat the test.

41. Re-engage the park brake and shutoff the engine.

42. Remove “Lock Out, Tag Out” plaque.

43. Return vehicle to service.