Wabash National Dry and Refrigerated Van Trailers, Operator'S Manual

Page: 23 / 42

19
brake System
The brake system consists of an air system
(reservoir, service valve, emergency valve, and air
lines), anti-lock brake system (ABS) (wheel speed
sensors, tone rings, warning lamp, electronic and
pneumatic control modules), and foundation brakes
(slack adjusters, S-cams, brake chambers, and
shoes or pads).
SySTeMS aND feaTUReS
brake air System
Trailer brakes are controlled by the tractor brake
system. The trailer brake system has two functional
systems: supply (emergency) and service.
The supply system connects with the tractor
through the red gladhand. It provides a constant
supply of air to the trailer and releases the parking
brakes and fills the trailer air reservoir.
The service system connects with the
tractor through the blue gladhand.
It provides a signal for trailer brake
application when tractor brakes are
applied. Service brakes apply when
the tractor brake pedal is depressed,
sending an air signal to the trailer
service valve. The relay valve sends
reservoir air to the trailer’s brake
chambers, which then actuate the
trailer brakes. When the tractor brake
pedal is released, the air signal vents
and the brakes are released.