Preventive Maintenance; Appendix A, Table A And The Column Entitled Vehicle - BENDIX AD-9 AIR DRYER Manual

SUPPLY
PORT
TURBO
CUTOFF
PISTON
EXHAUST
™
FIGURE 4 - AD-9 AIR DRYER TURBO CUTOFF
At the onset of the purge cycle, the downward travel of the
purge piston is stopped when the turbo cut-off valve (tapered
portion of purge piston) contacts its mating metal seat in
the purge valve housing. With the turbo cut-off valve seated
(closed position), air in the discharge line and AD-9
dryer inlet port is restricted from entering the air dryer. While
the turbo cut-off effectively prevents loss of turbo charger
boost pressure to the engine, some "seepage" of air may be
detected under certain conditions of compressor engine and
turbo charger operation, even so there will always be low
pressure trapped in the discharge line.

PREVENTIVE MAINTENANCE

Important: Review the warranty policy before performing
any intrusive maintenance procedures. An extended warranty
may be voided if intrusive maintenance is performed during
this period. Note: It is acceptable for the purge valve to be
maintained as necessary, i.e., the installation of a purge
valve maintenance kit, without voiding the warranty.
Because no two vehicles operate under identical conditions,
maintenance and maintenance intervals will vary. Experience
is a valuable guide in determining the best maintenance
interval for any one particular operation.
Every 900 operating hours or 25,000 miles or every three
(3) months:
1. Check for moisture in the air brake system by opening
reservoirs, drain cocks, or valves and checking for
presence of water. If moisture is present, the desiccant
may require replacement; however, the following
conditions can also cause water accumulation and
should be considered before replacing the desiccant:
4
PURGE
VALVE
CHECK
DISCHARGE VALVE
LINE ASSEMBLY
UPPER
BRACKET
STRAP
DESICCANT
CARTRIDGE
DESICCANT
BED
OIL
SEPARATOR
CONTROL
PORT
SUPPLY
PORT
TURBO
CUTOFF
PURGE VALVE
PISTON
FIGURE 5 - AD-9
™
air
A. An outside air source has been used to charge the
system. This air did not pass through the drying bed.
B. Air usage is exceptionally high and not normal for a
highway vehicle. This may be due to accessory air
demands or some unusual air requirement that does
not allow the compressor to load and unload
(compressing and non-compressing cycle) in a
normal fashion. Check for high air system leakage.
If the vehicle vocation has changed it may be
necessary to upgrade the compressor size. Refer to

Appendix A, Table A and the column entitled Vehicle

Vocation.
C. The air dryer has been installed in a system that
has been previously used without an air dryer. This
type of system will be saturated with moisture and
several weeks of operation may be required to dry it
out.
D. Location of the air dryer is too close to the air
compressor. Refer to Locating AD-9
Vehicle section and Appendix A, Table A, column 2
for discharge line length.
E. In areas where more than a 30 degree range of
temperature occurs in one day, small amounts of
water can accumulate in the air brake system due
to condensation. Under these conditions, the
presence of small amounts of moisture is normal
PURGE
HOUSING
VALVE
ASSEMBLY
™
AIR DRYER SECTIONAL VIEW
UPPER
BRACKET
HOUSING
LOWER
BRACKET
CHECK
VALVE
ASSEMBLY
DISCHARGE
PORT
™ Air Dryer On