217
2008 IMPERIAL
CHASSIS INFORMATION — 10
AIR DRYER
The air dryer, located between the frame rails
next to the transmission, removes moisture from
the compressed air system to prevent freezing
of brakes or other pneumatically operated
items. The three functions of the air dryer are
cooling,
fi
ltering and drying the system air. This
prevents valve and seal damage or wash away
of lubricants as well as freeze damage to the
system components.
Air Dryer Cycle:
The governor turns the compressor on
when the supply tank pressure drops below
cut-in pressure. Compressed air then passes
into the air dryer at the inlet port. Moisture-
laden air and contaminants pass through the
desiccant. Moisture is retained by the desiccant
and collects in the base of the dryer. When
the compressor reaches cut-out pressure
(approximately 145 psi) the purge valve opens
and the dryer purges and expels water collected
in the dryer base. The regeneration valve opens
sending a small charge of dry system air from
the front air tank back through the dryer. The
back
fl
ow dries the desiccant, preparing it for the
next cycle.
Air Dryer Components:
1. Purge Valve:
A valve located on
the bottom of the air dryer base that
remains open during a compressor
unload cycle to allow collected moisture,
condensation and contamination to expel
from the air dryer during the purge cycle.
2. Pressure Relief Valve:
Protects the air
dryer from over-pressurization.
3. Regeneration Valve:
Controls
regeneration of the desiccant by allowing
air from the supply and secondary tanks
to bypass the outlet check valve.
4. Heater Power Connection:
Provides 12
Volt DC power to the heating element.
In extreme cold, verify that the air dryer
heater is in good working order. The 100-watt
heater in the air dryer is controlled by ignition
power. The heater turns on below 45° F. and off
when the air dryer temperature is above 86° F.
The circuit breaker for the heater is located in
the rear electric bay.
WARNING:
Remove all pressure from the air system
before disconnecting any component,
including the desiccant cartridge.
Pressurized air can cause serious
personal injury.
Desiccant Cartridge
Warm, humid air from the
compressor condenses into either
water or water vapor. A desiccant-
type air dryer protects the air brake
system by drying moisture-laden
air before it passes through the
air reservoirs and into the brake
system. The replacement kit
contains one cartridge and one O-ring.
To Replace the Cartridge:
1. Loosen and remove the old cartridge.
Use a strap wrench, if necessary.
2. Remove and discard the O-ring from
the dryer base.
3.
Inspect
and clean the seal seat. Repair
any minor damage.
NOTE:
If the seats are damaged so badly that a
tight seal cannot be maintained, replace
the air dryer.
4. Install a new O-ring.
5. Lubricate the O-Ring on the stem with
a thin layer of grease.
6. Lubricate the cartridge seal with a thin
layer of grease.
7. Thread the replacement cartridge onto
the base until the seal touches the base.
Tighten the cartridge
ONE
additional
turn.
DO NOT OVERTIGHTEN
.
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