(9) Connect the trailer electrical power line; check
for proper operation of lights and, where applicable,
heating or refrigeration equipment.
(10) Raise the trailer parking legs, and release the
trailer parking brake, if so equipped.
(11) Before moving the tractor, check the brakes for
proper functioning and for adequate air pressure;
minimum operating air pressure is 60 pounds.
SEMITRAILER. To uncouple a truck-tractor from a
semitrailer, proceed as follows:
(1) Set the tractor parking brake.
(2) Apply pressure to the trailer brakes by
disconnecting the hose lines, as described above,
paragraph 7.2, step (5).
(3) Disconnect the trailer electrical power lines
and secure them to the tractor.
(4) Place wheel chocks (if used) in front and behind
the trailer wheels and set the trailer parking brake.
(5) Lower trailer parking legs; be sure the ground
is firm enough to prevent the parking legs from sinking.
(6) Place the fifth wheel hook lock handle in the
release position; move the tractor forward slightly,
leaving the trailer king pin partly in the fifth wheel slot.
( 7 ) Recheck the trailer supports; if trailer is
secure, move the tractor away from the trailer.