Air Supply System; Air Governor; Air Dryer - Monaco 2002 Diplomat Service Manual

Chassis Information
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AIR SUPPLY
SYSTEM

AIR GOVERNOR

OM090319.eps

AIR DRYER

1 0 • 2 6 6
The air compressing system on the motorhome is comprised of several
items: an air compressor, air governor, air dryer, a front air tank and a rear air
tank. The compressed air system operates several items, some of which
include brakes, suspension, air horns, air gauge and stepwell cover. The air
system is charged by a gear driven air compressor mounted on the engine. As
engine speed increases, compressed air output increases. When the air is
compressed, heat is generated. Heat dissipates as the air is discharged from
the compressor. Moisture condenses in the compressed air as it cools. The
moisture laden air then enters an air dryer where the air is filtered. The filtered
air charges the front air tank. The front air tank is divided in two halves: a
wet side and a dry side. The compressed air enters the wet side before entering
the dry side. A discharge line from the dry side of the front air tank charges
the rear air tank. The discharge lines use inline check valves to prevent back
flow of compressed air.
The pneumatically operated items are divided into two categories: brakes
and accessory air. Brakes have full use of supplied air pressure. Accessory air
items, such as air horns or stepwell covers, receive air through pressure
protection valves (PPV). The PPV will not allow compressed air flow until
approximately 60 psi. In the event of an air system problem, the pressure
protection valve will leave a reserve air charge for braking. Pressure protection
valves are installed for safety.
The air governor is located in the engine compartment and
performs two functions: regulating the air compressor to cut-in and
cut-out keeping the air system in the specified operating range of
105-120 psi, and sending an air "purge" signal to the Air Dryer.
Cut-in pressure of approximately 105 psi is factory preset from
the governor manufacturer and is not adjustable. Cut-out pressure is
calibrated to 120 psi. When cut-out pressure is reached, the gover-
nor will send an air purge signal to the Air Dryer. This opens the
purge port of the Air Dryer, expelling moisture. The purge action of
the Air Dryer is identified by the short release of air at the rear of
the motorhome.
The air dryer is located in the roadside compartment behind the rear wheel.
The air dryer removes moisture from the compressed air system. This is
important because if air contains moisture it can freeze and prevent operation
of brakes or other pneumatic operated items.
The air dryer has three functions: cooling, filtering and drying the air
going through the motorhome's air system. If an excessive amount of water is
present when performing the monthly air tank drain service it may be an
indication that the filter for the air dryer needs to be changed.
D I P L O M A T