176 OPERATION 5. Check that the fifth wheel height matches the height of the underside of the trailer. If the trailer is too high, use the landing gear to lower the trailer until fifth wheel and trailer height match. If the vehicle is equipped with an air suspension and the trailer is too low, use the air suspension control switch to exhaust air from the suspension air bags until fifth wheel and trailer height match.
CAUTION Failure to match fifth wheel height with trailer height will result in the trailer being improperly connected.
6. Back under the trailer slowly until the trailer king pin engages. Back slowly to avoid hitting the king pin too hard, and stop as soon as the king pin is locked into the fifth wheel. 7. If equipped with an air suspension, use the air suspension control switch to reinflate the suspension air bags. 8. Raise the trailer landing gear slightly off the ground. 9. With the trailer parking brakes applied, pull the tractor ahead slightly to ensure that the trailer is locked onto the tractor. 10. Push the trailer air supply valve (red octagonal knob) in to supply the trailer system with air pressure. With the air system at normal operating pressure, check the trailer air brake system for excessive leakage and proper operation. 11. Inspect the coupling to ensure the trailer is properly connected. Make sure there is no space between the fifth wheel and the trailer plate and that the fifth wheel jaws have closed around the shank of the king pin. Check that the locking lever is in the "lock" position and make sure the safety latch is in position over the locking lever. 12. After ensuring that the trailer is properly connected, raise the landing gear to its maximum height. 13. If wheel chocks were placed at the trailer wheels, remove the chocks and store.
CAUTION If equipped with an air suspension, do NOT operate the vehicle with the suspension air bags deflated. Always reinflate the suspension air bags after coupling or uncoupling a trailer.
