PREVOST H3-45 VIP Owner's Manual page 79

Rear Brake Air Pressure Gage (Primary System)
Indicates the rear brake air system pressure in psi. The normal
operating pressure is from 122 to 140 psi.
The low air pressure indicator LED on the gage and the STOP telltale
light illuminate when the rear brake air system pressure drops below 85
psi. An audible alarm will sound.
WARNING
The driver is responsible for monitoring the pressure as part of a
regular sweep of the instruments.
In the event of a pressure loss in the primary brake system, the drive
and tag axle service brakes will not function normally. It is critical to
bring the coach to a safe stop as quickly as possible.
If there is sufficient pressure in the secondary brake system,
modulated spring brake pressure (using the park brake chambers) will
be used to apply the drive axle brakes, proportional to the braking
pressure on the front axle. It must be noted this is an emergency and a
significant amount of secondary air pressure is lost with each
apply/release cycle. The spring brake modulation will only function
two or three times, depending on the amount of secondary air pressure
that was on hand when the primary brake pressure was lost.
Once the secondary air pressure drops below 60 psig, the park spring
brakes are fully applied and cannot be released until pressure is
restored.
Do not drive the coach when the brake air pressure is low.
DEF Level
Indicates the amount of DEF (Diesel Exhaust Fluid) remaining in the DEF tank.
The DEF tank is considered as being full when it contains 16 gallons (60 liters)
of DEF. DEF consumption will be approximately 2% of the diesel fuel
consumed.
CAUTION
DEF – Do not overfill
If an automatic nozzle is used for filling diesel exhaust fluid (DEF), do not add
further DEF after the nozzle has automatically shut off flow a first time. If such
nozzle is not available, use the DEF level gage on the instrument panel to
control the quantity during filling.
Diesel exhaust fluid DEF will begin to crystallize and freeze at 12°F (-11°C)
and expand by 7% when frozen. To allow expansion without damaging the
DEF tank, do not fill the tank with more than 16 gallons (60 liters).
PA-1619 Owner's Manual H3-45 VIP
Controls and Instruments 4-33
STOP telltale light