freightliner CENTURY CLASS S Driver Manual page 87

Steering and Brake Systems
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1. Turn Signal Lever
2. Trailer Brake Hand Control Valve
3. Hazard Warning Light Tab
Fig. 6.2, Steering Column-Mounted Controls (left-hand
drive shown)
WARNING
Do not use the trailer service brakes for parking;
they are not designed for this purpose. If air
bleeds out of the trailer air tank during parking,
the vehicle could roll, causing serious personal
injury or property damage.
The red octagonal-shaped knob
trol panel actuates the trailer air supply valve. After
the vehicle's air hoses are connected to a trailer, and
the pressure in both air systems is at least 65 psi
(448 kPa), the red knob must be pushed in. It should
stay in, to charge the trailer air supply system and to
release the trailer spring parking brakes. It must be
pulled out before disconnecting a trailer. It must also
be pulled out when operating a vehicle without a
trailer. If pressure in both air systems drops to 35 to
45 psi (242 to 310 kPa), the red knob automatically
pops out, exhausting the trailer air supply, and apply-
ing the trailer service or spring parking brakes.
The yellow diamond-shaped knob
control panel actuates the parking brake valve. Pull-
ing out the knob applies both the tractor and trailer
spring parking brakes and automatically causes the
trailer air supply valve knob to pop out.
CAUTION
Do not use the spring parking brakes if the ser-
vice brakes are hot, such as after descending a
steep grade. Also, do not use the spring parking
brakes during freezing temperatures if the ser-
6.3
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(Fig. 6.3) in the con-
(Fig. 6.3) in the
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1. Trailer Air Supply Valve Knob
2. Parking Brake Valve Knob
Fig. 6.3, Brake Valve Knobs
vice brakes are wet. To do so could damage the
brakes if hot, or cause them to freeze during cold
weather.
If the brakes are wet, drive the vehicle in low
gear and lightly apply the brakes to heat and dry
them. Allow hot brakes to cool before using the
spring parking brakes. Always chock the tires.
If the trailer is not equipped with spring parking
brakes, pulling out the yellow knob applies the tractor
spring parking brakes and the trailer service brakes.
When the tractor and trailer parking brakes (or trailer
service brakes) are both applied, the trailer brakes
are released by pushing in the red knob, leaving the
tractor parking brakes applied. Air pressure in the
primary or secondary reservoir must be at least 65
psi (447 kPa) before the tractor spring parking
brakes, or the trailer service or spring parking
brakes, can be released.
On trailers not equipped with spring parking brakes,
chock the trailer tires before disconnecting the truck
or tractor when parking just the trailer.
When parking a truck or tractor with a trailer (combi-
nation vehicle), and the trailer is not equipped with
spring parking brakes, apply the truck or tractor
spring parking brakes.
WARNING
If a trailer is not equipped with spring parking
brakes, do not park it or a combination vehicle
by pulling out only the trailer air supply valve
knob. This would apply only the trailer service
brakes. If air were to bleed from the trailer brake
system, the trailer brakes would release, possibly
causing an unattended runaway vehicle.
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