TM 9-2330-247-14&P
1-10.
EQUIPMENT DATA (Con't)
Frame:
Manufacturer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Johnson Corporation
Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Welded
S e c t i o n Ill. TECHNICAL PRINCIPLES OF O P E R A T I O N
Page
Page
Brake System . . . . . . . . . . . . . .
Lighting System . . . . . . . . . . . . . . . . . . . . .
LIGHTING SYSTEM
General Operation. The intervehicular cable on the trailer A-frame receives power from the towing vehicle.Thepower
is sent through a chassis wiring harness to provide power to operate the trailer lights.
Lights and Reflectors. Located on the right and left rear corners of the trailer, the composite lights contain four bulbs
that function as service taillights, stoplights, turn signals, blackout taillights, and blackout stoplights. Older model
trailers may have stoplight-taillight assemblies at each rear corner of the trailer and a separate blackout stoplight on
the right rear corner.
1-12. BRAKE SYSTEM
General Operation. Towing vehicle air pressure is sent through the emergency air line to the relay valve and then to the
pressure tank. When towing vehicle brakes are applied, air is sent through the service air line to the relay valve. The
relay valve then releases air from the pressure tank to the airbrake chamber. Air pressure behind the airbrake chamber
diaphragm pushes the piston in the master cylinder, which forces hydraulic fluid through the tubes to the wheel
cylinders. The wheel cylinders force the brakeshoes against the brakedrum. Brakeshoe and brakedrum friction slow,
stop, and hold the trailer until the brake pedal is released allowing applied air to vent.
Relay Valve. The relay valve speeds brake application by directly releasing air from the trailer pressure tank to the
airbrake chamber. This eliminates the loss of time that would result if air to operate the brakes had to travel directly from
the towing vehicle to the trailer airbrake chambers. In addition, the relay valve controls the flow of air to and from the
trailer pressure tank and automatically applies the brakes if the trailer breaks away from the towing vehicle or if there is
a serious leak in the emergency air line.
TA701026
