Volvo VNL Operator's Manual page 279

274 Brakes
Both circuits are piped into a dual brake
valve, which simultaneously applies front
and rear axle service brakes during each
brake application. In the event of a failure
in either one of the circuits, the other cir-
cuit becomes the emergency circuit for
applying the brakes.
The Master Warning Telltale and buzzer
alerts of a dangerous situation. Air pres-
sure is low and the remaining air volume
may not be enough for repeated braking.
The emergency brakes may engage,
causing a wheel lock-up, loss of vehicle
control and become a hazard to follow-
ing vehicles. Bring the vehicle to a
controled stop. Failure to follow these
precautions can result in loss of braking
control and serious personal injury or
death can occur as a result of a vehicle
accident.
An important feature of the brake system is
that an automatic spring brake application
does not take place as a result of an air loss
in only one of the two circuits. In this case,
brake control remains in the foot brake
valve. In each air pressure gauge, there is a
warning light connected to a low pressure
switch that comes on if air pressure goes
below 60 psi (420 kPa). At the same time,
the buzzer will sound and the main warning
telltale will come on. This pressure drop
warns the operator to make a manual emer-
gency stop before an automatic emergency
stop is made.
W3000638
Master Warning Telltale
W5000923