TRACTOR/SEMITRAILER COUPLING/UNCOUPLING (CONT)
b. To uncouple tractor/semitrailer, proceed as follows:
Do not uncouple tractor/semitrailer if tractor has less than normal operating air
pressure, approximately 100 - 120 psi (689.5 827 kPa) or semitrailer will not have
sufficient air pressure to apply or release brakes. Injury to personnel and damage
to equipment may result.
Do not uncouple a loaded semitrailer from the tractor for purposes of performing
maintenance tasks on the semitrailer or injury to personnel and damage to
equipment may result.
Make sure that the trailer band brake control (Johnny Bar) in the tractor cab is
completely released prior to applying the tractor parking brakes or loss of
semitrailer reserve air supply may occur.
(1) Using one spotter, maneuver tractor/semitrailer into an area for semitrailer parking. Once positioned for
parking, apply tractor parking brakes.
(2) Remove four wheel chocks (15) from gooseneck (16). Position wheel chocks (15) in front and behind each
outer set of dual tires (17) for right and left front bogies.
(3) Disconnect 12-pin electrical connector (14). Refer to appropriate tractor manual and restow electrical
connector to dummy connector on tractor. Be sure electrical connector (14) cover on semitrailer is closed.
(4) Disconnect emergency (red) air connector (12) and service (blue) air connector (13) from semitrailer. Stow
both air connectors on dummy connectors on tractor.
Ensure that vented dummy coupling is installed on the emergency (red) gladhand
prior to releasing brakes with the brake release valve. If a nonvented dummy
coupling is installed, the parking brakes cannot be reapplied and injury to
personnel may result.
(5) Install dummy connectors (18) to semitrailer emergency and service air connectors (12 and 13).
(7) Pull out handle of suspension shut-off valve (7) as far as possible to ADJUST position.
2-80 Change 1