Blocking Valve - Volvo 9700 US/CAN 2016 Driver's Handbook Manual

64 Instruments and controls

Blocking valve

The function of this valve is activate the
parking brake blocking by the pneumatic
control valve supply blocking, inhibiting the
parking brake valve function. Its happened,
if the pneumatic circuit pressures to low in
the bus, causing; that the blocking valve is
automatically activated (the valve is thrown).
To release the parking brake do the following:
1 Start the engine and charge the pneumatic
system of the bus (until the air brake
system warning lamp in the instrument
panel is turn OFF).
2 Press the blocking valve.
3 Put the parking brake control lever in the
brake release position (see the following
section on this manual: "Parking brake",
page 62).
Note: Once the blocking valve activated, the
parking brake can not release although the
parking brake control lever is in its forward
position (brake released). To release the
parking brake, it should restore the pneumatic
circuits pressure of the bus and press the
blocking valve.
T0015484