Ford F-650 2015 Owner's Manual page 142

AIR BRAKES
After starting the engine, give the air compressor time to build up the air
pressure to 60 psi (414 kPa) before moving your vehicle.
WARNING: Do not drive or continue to drive if the low air
pressure buzzer is sounding or the brake warning light is lit.
These warnings indicate that air pressure is not to normal operating
level. Continued use of the vehicle could result in loss of braking ability.
WARNING: Avoid repeated light application of the brake pedal.
This depletes air pressure faster and could result in loss of
braking capability.
When air pressure is insufficient (below 60 psi [414 kPa]), a
warning light illuminates and a buzzer sounds when the ignition
is in the on position.
This may happen because excessive brake applications are depleting the
system air pressure. If this condition occurs, stop driving your vehicle
until the compressor has fully recharged the air system.
WARNING: Do not move the vehicle when the air pressure is
insufficient because the brake system may be inoperative.
Select a gear ratio to help slow your vehicle before descending grades.
Supplementing with brakes, as required, help to safely slow the vehicle
and avoids overspeeding the engine.
2015 F-650/750 (f67)
Owners Guide gf, 2nd Printing, April 2014
USA (fus)
Brakes
Periodically check the air pressure
gauge while driving. Pressure should
range between approximately
100–125 psi (690–862 kPa). The air
compressor governor cut-in and
cutout pressure settings are set at
the factory and are not adjustable.
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