Operator`s manual

OPERATION
322
On vehicles equipped with the standard two valve system, the
operation of one valve together with the other permits the operator to
select the desired functions described below:
Parking Brake Release
VN and VHD models have engines equipped with engine electronic
control units (EECU). These have two features that may impact the
brake system. One is the anti-stall device in the EECU which senses
torque demand and automatically controls the engine to compensate
and maintain speed. On tractors equipped with parking brakes on only
one axle, the anti-stall device keeps the engine from stalling, allowing
the driver to pull away with the brakes dragging. This may result in
overheated brakes and damaged wheel hubs.
Continual dragging of the brakes will cause brakes
to overheat. This may lead to wheel end fire. To
avoid overheating, make sure both parking brake
knobs are pushed in before driving off.
If the yellow knob is pulled out and the red knob is pushed in, a
condition is created where the trailer parking brakes are not applied
and only the single drive axle brakes are applied. In this condition, the
vehicle can be driven away. Therefore, it is very important that the
driver make sure the yellow AND red knobs are pushed in all the way
before driving the vehicle.
Red Valve (Trailer
Air Supply)
Yellow Valve
(System Park) Function (Mode)
Out Out System Park
In Out Trailer Charge
In In Normal Running
Out In Bobtail
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