User Manual

the parking (spring) brakes of the
vehicle or of the vehicle-trailer
combinations. If the air system is
being charged from zero pressure,
the parking brake valve will not hold in
the release position until the system
pressure exceeds 60 psi (414 kPa),
which is the pressure required to
override the load of this valve's
plunger return spring.
Trailer Supply
V
alve
The Red octagonal-shaped knob
protects the vehicle system; it
functions in conjunction with the
parking brake valve (yellow). The
trailer supply valve is responsible for
synchronizing the vehicle and trailer
parking and emergency brakes. If the
air system is being charged from zero
pressure, the trailer supply valve will
not hold in the applied position until
the system pressure exceeds 50 psi
(345 kPa). It automatically pops out
and exhausts air if supply air pressure
drops below 60 psi (414 kPa).
Vehicle
Protection
Valve
The functions of this valve are to (1)
receive all pneumatic signals
pertinent to the operation of the trailer
brake system, (2) transmit these
signals to the trailer, and (3) protect
the vehicle air supply in case of
separation of the air lines connecting
the vehicle to the trailer.
Brake Safety and
Emergency
WARNING
Do not operate the vehicle in the event
of
a malfunction in any air circuit. The
vehicle should not be operated until
the system is repaired and both brak-
ing circuits, including all pneumatic
and mechanical components, are
working properly. Loss of system air
can cause the service brakes to not
function resulting in the sudden appli-
cation of the spring brakes causing
wheel lock-up, loss of control, or over-
take by following vehicles. Failure to
comply may result in property damage,
personal injury, or death.
• If pressure is lost in the vehicle
front or rear circuit, the "check"
valves isolate the unaffected circuit,
allowing this circuit to continue
normal operation. The trailer
brakes are still functional.
• If air pressure is lost in the trailer
supply/park circuit, and the
pressure drops below 60 psi (414
kPa), the trailer spring brakes are
automatically applied, and the
vehicle air pressure circuits are
unaf
fected.
• If air pressure is lost in the trailer
brake service circuit, and the
pressure in the vehicle front and
rear circuits drops below 60 psi
(414 kPa), the vehicle and trailer
spring brakes are automatically
applied.
ABS Warning Lamp
The ABS warning lamp will come on briefly,
then go off, when the key switch is first
turned on. If the lamp remains ON until a
speed of 4 mph (6 km/h) is reached, then
goes OFF, there may be a stored fault
code. If the lamp remains ON when a
speed in excess of 4 mph (6 km/h) is
reached, there may be an active fault in the
ABS system.
DRIVING - Brake Safety and Emergency
Y53-6113-1A1 (11/20) 141
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