Volvo VHD - Manual (Page 236)

230 Brakes
Parking Brake Release
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 de-
vice in the EECU which senses torque
demand and automatically controls the en-
gine 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 dam-
aged wheel hubs.
WARNING
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.
‘
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If both the yellow and the red knobs are
pulled out, the combined force of the two
trailer axles and the tractor drive axle is
sufficient to stall the engine. However, 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 ap-
plied 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 makes sure the
yellow and the red knobs are pushed all the
way in before driving the vehicle.
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