Bendix® AD-9™ Air Dryer
SD-08-2412
END COVER
CHECK
VALVE
ASSEMBLY
FIGURE 1 - AD-9
DELIVERY PORT
EXTENDED PURGE AD-9™ AIR DRYER STANDARD AD-9™ AIR DRYER
™
DESCRIPTION
WIRING HARNESS
CONNECTION
AIR DRYER MODELS
OUTER
SHELL
CONTROL
PORT
SUPPLY
PORT
END COVER
CHECK
VALVE
ASSEMBLY
DELIVERY PORT
OUTER
SHELL
CONTROL
PORT
SUPPLY
PORT
WIRING HARNESS
CONNECTION
The function of the AD-9™ air dryer is to collect and remove
air system contaminants in solid, liquid and vapor form before
they enter the brake system. It provides clean, dry air to the
components of the brake system which increases the life of
the system and reduces maintenance costs. Daily manual
draining of the reservoirs is eliminated.
The AD-9™ air dryer consists of a desiccant cartridge and a
die cast aluminum end cover secured to a cylindrical steel
outer shell with eight cap screws and nuts. The end cover
contains a check valve assembly, a safety valve, three
threaded air connections and the purge valve housing
assembly. The removable purge valve housing assembly
incorporates a purge valve mechanism and a turbo charger
cut-off feature that is designed to prevent loss of engine
“turbo” boost pressure during the purge cycle of the AD-9
air dryer. For ease of serviceability, the desiccant cartridge
and discharge check valve assembly are screw in type. The
purge valve housing assembly, which includes the heater
and thermostat assembly, and the discharge check valve
assembly , is serviceable from the exterior of the air dryer,
while servicing the screw-in desiccant cartridge requires
removal of the air dryer assembly from the vehicle.
The AD-9™ air dryer has three female pipe thread air
connections and each is identified as follows:
Port l.D. Function/Connection
CON 4............... Control Port
(purge valve control and turbo cut-off).
SUP 1 1 ............. Supply Port (air in).
DEL 2 ............... Delivery Port (air out).
™
1
DESICCANT
CARTRIDGE
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ORIFICE
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COMPRESSORGOVERNOR
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FIGURE 2 - AD-9™ AIR DRYER CHARGE CYCLE
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RESERVOIR
ENGINE
TURBO
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CONTROL
PORT
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SUPPLY
PORT
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DESICCANT
BED
OIL
SEPARATOR
PURGE
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VALVE
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EXHAUST
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ELEMENT
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HEATER
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SUMP
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DELIVERY
PURGE
VOLUME
CHECK
VALVE
ASSEMBLY
PORT
OPERA TION OF THE AD-9™ AIR DRYER
The AD-9™ air dryer alternates between two operational
modes or “cycles” during operation: the charge cycle and
the purge cycle. The following description of operation is
separated into these “cycles” of operation.
CHARGE CYCLE (refer to Figure 2)
When the compressor is loaded (compressing air)
compressed air, along with oil, oil vapor, water and water
vapor flows through the compressor discharge line to the
supply port of the air dryer end cover . As air travels through
the end cover assembly , its direction of flow changes several
times, reducing the temperature, causing contaminants to
condense and drop to the bottom or sump of the air dryer
end cover.
After exiting the end cover , the air flows into the desiccant
cartridge. Once in the desiccant cartridge air first flows
through an oil separator which removes water in liquid form
as well as oil and solid contaminants.
Air exits the oil separator and enters the desiccant drying
bed. Air flowing through the column of desiccant becomes
progressively drier as water vapor adheres to the desiccant
material in a process known as “adsorption”. The desiccant
cartridge using the adsorption process typically removes
95% of the water vapor from the pressurized air.
The majority of dry air exits the desiccant cartridge through
its integral single check valve to fill the purge volume between
the desiccant cartridge and outer shell. Some air will also
exit the desiccant cartridge through the purge orifice adjacent
to the check valve.
Dry air flows out of the purge volume through the single
check valve assembly and out the delivery port to the first
(supply) reservoir of the air system.
The air dryer will remain in the charge cycle until air brake
system pressure builds to the governor cutout setting.
PURGE CYCLE (refer to Figure 3)
When air brake system pressure reaches the cutout setting
of the governor, the compressor unloads (air compression
stopped) and the purge cycle of the air dryer begins. When
the governor unloads the compressor, it pressurizes the
compressor unloader mechanism and line connecting the
2
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VALVE
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HEATER
ELEMENT
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DESICCANT
CARTRIDGE
DESICCANT
BED
OIL
SEPARATOR
CONTROL
PORT
COMPRESSORGOVERNOR
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RESERVOIR
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ENGINE
TURBO
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SUPPLY
PORT
TURBO
CUTOFF
PISTON
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PURGE
VALVE
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EXHAUST
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ORIFICE
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SUMP
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PURGE
VOLUME
CHECK
VALVE
ASSEMBLY
DELIVERY
PORT
FIGURE 3 - AD-9™ AIR DRYER PURGE CYCLE
governor unloader port to the AD-9™ air dryer end cover control
port. The purge piston moves in response to air pressure
causing the purge valve to open to atmosphere and (partially)
closing off the supply of air from the compressor , this will be
further discussed in the section covering the turbo cut-off
feature. Contaminants in the end cover sump are expelled
immediately when the purge valve opens. Also, air which
was flowing through the desiccant cartridge changes direction
and begins to flow toward the open purge valve. Oil and solid
contaminants collected by the oil separator are removed by
air flowing from the desiccant drying bed to the open purge
valve.
The initial purge and desiccant cartridge decompression lasts
only a few seconds and is evidenced by an audible burst of
air at the AD-9™ air dryer exhaust.
The actual reactivation of the desiccant drying bed begins
as dry air flows from the purge volume through the desiccant
cartridge purge orifice and into the desiccant drying bed.
Pressurized air from the purge volume expands after passing
through the purge orifice; its pressure is lowered and its
volume increased. The flow of dry air through the drying bed
reactivates the desiccant material by removing the water
vapor adhering to it. Generally 15-30 seconds are required
for the entire purge volume of a standard AD-9™ air dryer to
flow through the desiccant drying bed.
The end cover single check valve assembly prevents air
pressure in the brake system from returning to the air dryer
during the purge cycle. Af ter the 30 second purge cycle is
complete, the air dryer is ready for the next charge cycle to
begin.
The purge valve will remain open after the purge cycle is
complete and will not close until air brake system pressure
is reduced and the governor signals the compressor to
charge.
TURBO CUT-OFF FEATURE (Refer to Figure 4)
The primary function of the turbo cut-off valve is to prevent
loss of engine turbocharger air pressure through the AD-9
air dryer in systems where the compressor intake is
connected to the engine turbocharger . The turbo cut-off valve
also reduces the “puffing” of air out the open exhaust when
a naturally aspirated, single cylinder compressor equipped
with an inlet check valve is in use.
™
3
UPPER
BRACKET
STRAP
UPPER
BRACKET
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SUPPLY
PORT
TURBO
CUTOFF
PISTON
FIGURE 4 - AD-9™ AIR DRYER TURBO CUTOFF
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EXHAUST
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PURGE
VALVE
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DISCHARGE
LINE
CHECK
VALVE
ASSEMBLY
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™ air
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:
DESICCANT
CARTRIDGE
DESICCANT
BED
OIL
SEPARATOR
CONTROL
PORT
SUPPLY
PORT
TURBO
CUTOFF
PISTON
FIGURE 5 - AD-9
PURGE VALVE
HOUSING
ASSEMBLY
™
AIR DRYER SECTIONAL VIEW
PURGE
VALVE
HOUSING
LOWER
BRACKET
CHECK
VALVE
ASSEMBLY
DISCHARGE
PORT
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™ Air Dryer On
Vehicle section and Appendix A, T able 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
4
and should not be considered as an indication that
the dryer is not performing properly .
Note: A small amount of oil in the system may be normal
and should not, in itself, be considered a reason to
replace the desiccant; oil stained desiccant can function
adequately.
2. Check mounting bolts for tightness. Retorque to 270385 inch pounds.
3. Perform the Operation & Leakage Tests listed in this
publication.
Every 10,800 hours; 300,000 miles or 36 months:
1. Rebuild the air dryer including the desiccant cartridge.
Note: The desiccant change interval may vary from vehicle
to vehicle. Although typical desiccant cartridge life is three
years, many will perform adequately for a longer period of
time. In order to take maximum advantage of desiccant life
and assure that replacement occurs only when necessary ,
it is important that Operation & Leakage T ests be performed.
WARNING!
This air dryer is intended to remove moisture and other
contaminants normally found in the air brake system.
Do not inject alcohol, anti-freeze, or other de-icing
substances into or upstream of the air dryer. Alcohol
is removed by the dryer, but reduces the effectiveness
of the device to dry air. Use of other substances can
damage the air dryer and may void the warranty.
OPERATION & LEAKAGE TESTS
1. Test the outlet port check valve assembly by building
the air system to governor cut-out and observing a test
air gauge installed in the #1 reservoir. A rapid loss of
pressure could indicate a failed outlet port check valve.
This can be confirmed by bleeding the system down,
removing the check valve assembly from the end cover,
subject air pressure to the unit and apply a soap solution
to the check valve side. Leakage should not exceed a 1”
bubble in 1 second.
2. Check for excessive leakage around the purge valve.
With the compressor in loaded mode (compressing air),
apply a soap solution to the purge valve housing
assembly exhaust port and observe that leakage does
not exceed a 1” bubble in 1 second. If the leakage
exceeds the maximum specified, service the purge valve
housing assembly .
3. Close all reservoir drain cocks. Build up system pressure
to governor cut-out and note that AD-9™ air dryer purges
with an audible escape of air. “Fan” the service brakes
to reduce system air pressure to governor cut-in. Note
that the system once again builds to full pressure and is
followed by an AD-9™ air dryer purge.
™
AD-9
AIR DRYER
™
AD-9
END COVER
SIDE VIEW END VIEW
A two lead, 12 inch, wire harness with attached weather
resistant connector is supplied with all retrofit and
replacement AD-9
leads of the wire harness to the engine kill or ignition
switch. The remaining lead of the wire harness must be
connected to a good vehicle ground. A fuse should be
installed in the power carrying wire; install a 10 amp fuse
for 12 volt heaters and a 5 amp fuse for a 24 volt heater.
Use 14 AWG wire if it is necessary to lengthen the wire
harness provided.
Make certain all wire splices are waterproofed.
Tie wrap or support all electrical wire leading to the
™
air dryer.
AD-9
FIGURE 6 - HEA TER AND THERMOSTAT CONNECTOR
™
air dryers. Connect one of the two
LOWER
MOUNTING
BRACKET
FEMALE
CONNECTOR
MALE
CONNECTOR
LATCH MUST BE
INSERTED UNTIL
IT SNAPS OVER
TAB ON MATING
CONNECTOR
4. Check the operation of the safety valve by pulling the
exposed stem while the compressor is loaded
(compressing air). There must be an exhaust of air while
the stem is held and the valve should re-seat when the
stem is released.
5. Check all lines and fittings leading to and from the air
dryer for leakage and integrity .
6. Check the operation of the end cover heater and
thermostat assembly during cold weather operation as
follows:
A. Electric Power to the Dryer
With the ignition or engine kill switch in the ON
position, check for voltage to the heater and
thermostat assembly using a voltmeter or test light.
Unplug the electrical connector at the air dryer and
place the test leads on each of the pins of the male
connector. If there is no voltage, look for a blown
fuse, broken wires, or corrosion in the vehicle wiring
harness. Check to see if a good ground path exists.
5
B. Thermostat and Heater Operation
Turn off the ignition switch and cool the end cover
assembly to below 40 degrees Fahrenheit. Using an
ohmmeter, check the resistance between the
electrical pins in the female connector. The resistance
should be 1.5 to 3.0 ohms for the 12 volt heater
assembly and 6.8 to 9.0 ohms for the 24 volt heater
assembly. Note: Some early models of the AD-9
air dryer will have resistance readings of 1.0 to 2.5
ohms for the 12 volt heater assembly and 4.8 to 7.2
ohms for the 24 volt heater assembly. If the
resistance is higher than the maximum stated,
replace the purge valve housing assembly, which
includes the heater and thermostat assembly .
Warm the end cover assembly to over 90 degrees
Fahrenheit and again check the resistance. The
resistance should exceed 1000 ohms. If the
resistance values obtained are within the stated
limits, the thermostat and heater assembly is
operating properly. If the resist ance values obtained
are outside the stated limits, replace the purge valve
housing assembly, which includes the heater and
thermostat assembly .
REBUILDING THE AD-9™ AIR DRYER
GENERAL
If, after completing the routine operation and leakage tests,
it has been determined that one or more components of the
air dryer requires replacement or maintenance, refer to the
following list to find the appropriate kit(s).
When rebuilding or replacing components of the air dryer
use only genuine Bendix parts. For ease in servicing the
AD-9™ air dryer desiccant cartridge assembly, it is
recommended that the air dryer be removed from the vehicle.
MAINTENANCE KITS A V AILABLE:
5005037 Hard Seat Purge Valve Housing Maintenance Kit
5005893 Soft Seat Purge Valve Housing Maintenance Kit
These kits contain the parts necessary to rebuild
the air portion of the purge valve housing and do
not include the heater and thermostat.
107796 Remanufactured Desiccant Cartridge
Replacement Kit
This kit contains the parts necessary to change
the desiccant cartridge only .
107794 Desiccant Cartridge Replacement Kit
This kit contains the parts necessary to change
the desiccant cartridge only .
107799 End Cover Check Valve Assembly Replacement
3/4 inch thread size.
107800 End Cover Check Valve Assembly Replacement
1/2 inch thread size.
800405
5004341
5004479
™
5004339 Service New Purge Valve Housing Assembly -
5004338 Service New Purge Valve Housing Assembly - Soft
5004342
5004480 Service New Valve Housing Assembly - Hard Seat
5004340 Service New Purge V alve Housing Assembly - DLU
107695 Complete Mounting Bracket Kit
Service New Purge V alve Housing Assembly Soft Seat (w/heater and thermo.) 12 volt
system.
Remanufactured Exchange Purge Valve
Housing Assembly - Soft Seat (w/heater and
thermo.) 12 volt system.
Service New Purge Valve Housing Assembly Hard Seat
(w/heater and thermo.) 12 volt system.
DLU (w/heater and thermo.) 12 volt system.
Seat (w/heater and thermo.) 24 volt system.
Remanufactured Exchange Purge V alve Housing
Assembly - Soft Seat (w/heater and thermo.) 24
volt system.
(w/heater and thermo.) 24 volt system.
(w/heater and thermo.) 24 volt system.
This kit contains the upper and lower brackets as
well as the necessary hardware items to mount
them.
GENERAL SAFETY GUIDELINES
WARNING! PLEASE READ AND FOLLOW
THESE INSTRUCTIONS TO AVOID
PERSONAL INJURY OR DEATH:
When working on or around a vehicle, the following
general precautions should be observed at all times.
1. Park the vehicle on a level surface, apply the
parking brakes, and always block the wheels.
Always wear safety glasses.
2. Stop the engine and remove ignition key when
working under or around the vehicle. When
working in the engine compartment, the engine
should be shut off and the ignition key should be
removed. Where circumstances require that the
engine be in operation, EXTREME CAUTION should
be used to prevent personal injury resulting from
contact with moving, rotating, leaking, heated or
electrically charged components.
3. Do not attempt to install, remove, disassemble or
assemble a component until you have read and
thoroughly understand the recommended
procedures. Use only the proper tools and observe
all precautions pertaining to use of those tools.
4. If the work is being performed on the vehicle’s air
brake system, or any auxiliary pressurized air
systems, make certain to drain the air pressure from
all reservoirs before beginning ANY work on the
vehicle. If the vehicle is equipped with an AD-IS
air dryer system or a dryer reservoir module, be
sure to drain the purge reservoir .
®
6
28
26
22
27
21
23
12
END
COVER
25
24
19
17
1
20
17
18
15
8
11
2
17
7
6
16
5
14
10
13
9
3
4
ITEM DESCRIPTION
1 O-RING
2 PURGE VALVE GUIDE
3 1/4" TAPPING SCREW
4 SHOULDER BOLT
5 O-RING
6 O-RING - (NOT USED ON DLU MODELS)
7 O-RING
8 PURGE VALVE ASSEMBLY (COMPLETE)
9 PURGE VALVE HOUSING
10 HARD SEAT PURGE PISTON
11 PURGE VALVE
12 SAFETY VALVE
13 SPRING
14 QUAD-RING
15 DELIVERY CHECK VALVE ASSEMBLY
16 3/8" CAP SCREW
17 3/8" WASHER
18 3/8" CAP SCREW (LONG)
19 LOCKNUT
20 LOWER MOUNTING BRACKET
21 O-RING
22 DESICCANT CARTRIDGE ASSEMBLY (COMPLETE)
23 O-RING
24 OUTER HOUSING
25 5/16" X 4-1/2" UPPER BRACKET CAP SCREW
26 UPPER MOUNTING BRACKET STRAP
27 UPPER MOUNTING BRACKET SADDLE
28 SLEEVE NUT
FIGURE 7 - AD-9™ AIR DRYER ASSEMBLY
7
5. Following the vehicle manufacturer’s
recommended procedures, deactivate the electrical
system in a manner that safely removes all
electrical power from the vehicle.
6. Never exceed manufacturer’s recommended
pressures.
7. Never connect or disconnect a hose or line
containing pressure; it may whip. Never remove a
component or plug unless you are certain all
system pressure has been depleted.
8. Use only genuine Bendix® replacement parts,
components and kits. Replacement hardware,
tubing, hose, fittings, etc. must be of equivalent
size, type and strength as original equipment and
be designed specifically for such applications and
systems.
9. Components with stripped threads or damaged
parts should be replaced rather than repaired. Do
not attempt repairs requiring machining or welding
unless specifically stated and approved by the
vehicle and component manufacturer.
10. Prior to returning the vehicle to service, make
certain all components and systems are restored
to their proper operating condition.
1 1. For vehicles with Antilock T raction Control (ATC),
the ATC function must be disabled (ATC indicator
lamp should be ON) prior to performing any vehicle
maintenance where one or more wheels on a drive
axle are lifted off the ground and moving.
AD-9™ AIR DRYER REMOVAL
1. Park the vehicle on a level surface and prevent movement
by means other than the brakes.
2. Drain all reservoirs to 0 p.s.i. (0 kPa).— Caution:
Compressor discharge line may still contain residual
pressure.
3. Identify and disconnect the three air lines from the end
cover and note the position of end cover ports relative to
the vehicle.
4. Unplug the vehicle wiring harness from the heater and
thermostat assembly connector on the purge valve
housing assembly .
5. Loosen the 5/16" X 4-1/2" hex cap screw (25) securing
the upper mounting strap (26).
6. Remove, retain and mark the two 3/8" end cover cap
screws (18), lock nuts (19) and four special washers
(17) that retain the lower mounting bracket (20) to the
end cover, also mark these two holes of the end cover.
(These bolts are longer than the other 6 bolts.)
7. Remove the AD-9™ air dryer from its mounting brackets
on the vehicle.
DISASSEMBLY
The following disassembly and assembly procedure is
presented for reference purposes and presupposes that a
major rebuild of the AD-9™ air dryer is being undertaken.
Several replacement parts and maintenance kits are available
which do not require full disassembly. The instructions
provided with these parts and kits should be followed in lieu
of the instructions presented here. Refer to Figure 7 during
disassembly.
Caution: While performing service on the AD-9™ air
dryer, it is not recommended that a clamping device
(vise, C-clamp, etc.) be used to hold any die cast
aluminum component as damage may result. To hold
the end cover, install a pipe nipple in the supply port
and clamp the nipple into a vise.
1. Using an adjustable wrench or an 1-3/4" socket, remove
the delivery check valve assembly (15) and o-ring (1).
Remove the o-ring (1) from the check valve assembly.
2. Remove the three 1/4" self tapping screws (3) that secure
the purge valve housing assembly to the end cover
assembly. Pull the purge valve housing assembly (8) out
of the end cover assembly. Remove the o-rings (5, 6 & 7)
from the exterior of the purge valve housing assembly.
(O-ring item 6 is not included in DLU models.) Note: the
o-rings may be lodged in the end cover bores, if so, they
must be removed.
3. Purge Valve (8) Disassembly:
Note: Removal of the piston from the purge valve housing
assembly requires a tool to hold the head of the purge
piston while unscrewing the purge valve shoulder bolt
(4). If an extended type exhaust cover is in use to
accommodate the attachment of an exhaust hose, the
exhaust cover must be carefully peeled off of the purge
valve housing (9). Use a thin flat blade to pry the
exhaust cover off, taking care not to damage the
potting material (RTV sealant) under the cover. To
remove the piston (10) from the purge valve housing
assembly (9)(9) use a twelve point 1/4" socket to hold
the head of the shoulder bolt (4).
A. Remove the shoulder bolt (4) from the bottom of the
purge valve housing assembly (8) while securing the
top of the purge piston (10) using the two opposing
cast indentations and a tool. Remove the purge guide
(2) and purge valve (1 1) from the purge valve housing.
B. Remove the purge piston (10) and return spring (13)
from the opposite end of the purge valve housing.
Remove the quad ring (14) from the purge piston (10).
C. Heater and Thermostat Assembly Replacement.
Caution: Do not attempt to remove this assembly ,
as it will be damaged during the removal process
and is not available as a service part. If the heater
and thermostat are defective, replace the entire purge
valve housing assembly which includes these items.
8
4. Remove the remaining six 3/8" cap screws (16), lock
nuts (19) and twelve special washers (17) that secure
the end cover to the housing (24). Separate the end cover
and desiccant cartridge (22) from the housing (24).
5. Remove the end cover to outer housing o-ring (23).
6. Do not remove the safety valve (12) from the end cover
unless it has been proven defective. If replacement is
required, apply thread sealant or Teflon® tape on the
threads of the replacement valve and torque to 120-400
in. Ibs.
7. Place a strap or chain wrench around the desiccant
cartridge (22) so that it is approximately 2-3 inches away
from the end cover. Rot ate the cartridge counterclockwise
until it completely separates from the end cover . Note:
A substantial torque (up to 50 lb. ft.) may be required to
perform this disassembly .
8. Remove the desiccant cartridge o-ring (21) from the end
cover.
CLEANING & INSPECTION
1. Using mineral spirits or an equivalent solvent, clean and
thoroughly dry all metal parts.
2. Inspect the interior and exterior of all metal parts that
will be reused for severe corrosion, pitting and cracks.
Superficial corrosion and/or pitting on the exterior portion
of the upper and lower body halves is acceptable.
3. Inspect the bores of both the end cover and the purge
valve housing for deep scuffing or gouges.
4. Make certain that all purge valve housing and end cover
passages are open and free of obstructions.
5. Inspect the pipe threads in the end cover . Make certain
they are clean and free of thread sealant.
6. Inspect the purge valve housing bore and seats for
excessive wear and scuffing.
7. Inspect the purge valve piston seat for excessive wear.
8. Inspect all air line fittings for corrosion. Clean all old
thread sealant from the pipe threads.
9. All o-rings removed should be discarded and replaced
with new o-rings provided in appropriate kit(s).
the bore of the purge valve housing. Insert the purge
piston (10) into the I.D. of the return spring. Place
the purge valve guide (2) onto the shoulder bolt (4)
followed by the purge valve (1 1). Using a ratchet or
wrench, screw the purge valve, purge valve guide and
shoulder bolt into the purge housing until it bottoms.
This will require a tool to hold the top of the purge
piston from rotating as the shoulder bolt is screwed
into the bottom of the purge piston to complete the
purge valve assembly (8). T orque the shoulder bolt
to 60-90 in. lbs.
B. Install the o-rings (5, 6 and 7) on the purge valve
housing placing each in its appropriate location. Note
o-ring (6) is not used on DLU models. If the exhaust
cover was removed during disassembly , install it on
the purge valve housing assembly (8) making certain
the “bubble” portion is positioned over the thermostat.
Install the assembled purge valve housing (8) in the
end cover making certain to orient both parts such
that the connector is approximately 10 degrees
clockwise from the supply port, while making certain
the purge valve housing is fully seated against the
end cover. Secure the purge valve housing to the
end cover using the three 1/4" self-tapping screws
(3). St art all three screws by hand then torque to 5080 in. Ibs.
2. Install the o-ring (1) on the check valve assembly (15),
then install the assembly in the end cover .
6
4
2
5
Any component exhibiting a condition described in step 1
to 8 should be replaced.
ASSEMBLY
Prior to assembly , coat all o-rings, o-ring grooves, and bores
with a generous amount of the lubricant included in the
maintenance kit. Refer to Figure 7 during assembly unless
otherwise advised.
1. Purge V alve Housing Assembly
A. Install the quad-ring (14) in its groove on the O.D. of
the purge piston (10). Place the return spring (13) in
1&9
7
FIGURE 8 - END COVER TO HOUSING TORQUE PATTERN
3
8
9
3. Install the desiccant cartridge o-ring (21) in its groove in
the end cover. Using a light coat of lubricant (included in
kit), lubricate the bottom of the desiccant cartridge in
the area that will contact the o-ring (21) and end cover .
Screw the desiccant cartridge into the end cover until
contact is made between it and the o-ring. Using a strap
or chain wrench positioned 2-3" from the bottom of the
cartridge, turn the desiccant cartridge clockwise 180225 degrees beyond the position where initial contact
was made between the cartridge and end cover o-ring.
T orque should not exceed 50 f t. Ibs.
4. Install the end cover outer housing o-ring (23) on the
shoulder in the end cover. Place the housing (24) over
the desiccant cartridge and align the holes. Install the
six 3/8" cap screws (16), lock nuts (19) and twelve special
washers (17) making certain they are in the proper
position as marked during disassembly . The two longer
3/8" cap screws (18) will be used to secure the AD-9
air dryer to its mounting bracket. Tighten the six cap
screws and nuts in a star pattern in a fashion similar to
Figure 8; depending on lower bracket location. Torque
to 270-385 in. Ibs. (Refer to Fig. 8.) Note: The two
remaining bolt holes in the end cover and two 3/8" cap
screws must be the ones marked during disassembly
to assure proper orientation of the ports and adequate
length of the cap screws.
INSTALLATION
1. Install the assembled AD-9™ air dryer back onto the
vehicle by slipping it into the upper mounting bracket.
Align the two unused holes in the end cover with the
bottom mounting bracket such that the bottom bracket
supports the air dryer. The AD-9™ air dryer end cover
should rest on the bracket. Using the remaining two 3/
8" cap screws (18), four special washers (17), and two
lock nuts (19), secure the air dryer to the lower bracket.
Tighten, then torque the two remaining cap screws to
270-385 in. Ibs.
2. Tighten the 5/16" X 4-1/2" hex cap screw (25) and nut
(28) on the upper mounting bracket saddle (27) and strap
(26). T orque to 80-120 in. Ibs.
3. Reconnect the three air lines to the proper ports on the
end cover (identified during disassembly).
4. Reconnect the vehicle wiring harness to the AD-9™ air
dryer heater and thermostat assembly connector by
plugging it into the air dryer connector until its lock tab
snaps in place.
5. Before placing vehicle back into service, perform the
Operation and Leakage Tests st ated elsewhere in this
manual.
RETROFITTING THE AD-9™ AIR DRYER
GENERAL
The following retrofit instructions are presented for reference
purposes only since Bendix aftermarket retrofit and
replacement air dryers are packaged with the most up-todate installation instructions. The instructions packaged with
the AD-9™ air dryer should be followed in lieu of those
presented here.
The preceding portion of this manual deals with “in-service”
repair and/or replacement of the AD-9
of the manual that follows is concerned with installing an
AD-9™ air dryer on a vehicle not previously equipped with
one.
VEHICLE APPLICATION REQUIREMENTS
The basic application requirements presented here apply to
™
a standard air dryer installation. The majority of highway
vehicles in use today will meet these basic requirements
however, some may not. Examples of vehicles that may not
meet the requirements include, bulk trailer unloading
operations and other high air consumption/continuous flow
systems. While the AD-9™ air dryer can be used on these
vehicles the standard installation procedure presented in
this manual may require modification to assure proper
operation and service life. Consult your local authorized
Bendix parts outlet or sales representative for additional
information.
1. Charge Cycle Time - The AD-9™ air dryer is designed to
provide clean, dry air for the brake system. When a
vehicle’s air system is used to operate non-brake air
accessories it is necessary to determine that during
normal, daily operation the compressor should recover
from governor “cut-in” to governor “cut-out” (usually 100
psi to 120 psi) in 90 seconds or less at engine RPMs
commensurate with the vehicle vocation. If the recovery
time consistently exceeds this limit, it may be
necessary to “bypass” the air accessory responsible for
the high air usage. Consult your local authorized Bendix
parts outlet or sales representative for additional
information.
2. Purge Cycle Time - During normal vehicle operation, the
air compressor must remain unloaded for a minimum
of 20 seconds for the standard AD-9™ air dryer or 30
seconds for the Extended Purge model. These
minimum purge times are required to ensure complete
regeneration of the desiccant material. If the purge time
is occasionally shorter than the times specified, no
permanent ill effect should be expected, however , if the
purge time is consistently less than the minimum, an
accessory by-pass system must be installed.
3. European Air Brake Systems - Brake systems that
incorporate compressors without integral unloading
™
air dryer. The portion
10
mechanisms and/or utilize a compressor discharge line
unloader valve have special AD-9™ air dryer installation
requirements. Consult your local authorized Bendix parts
outlet or sales representative for additional information.
4. Air Compressor Size - Although the AD-9™ air dryer can
be used in conjunction with larger compressors, it was
designed primarily for units rated for up to 17 CFM. It is
recommended that when using the AD-9™ air dryer with
a compressor which has a rated displacement exceeding
17 CFM that an authorized Bendix parts outlet or Bendix
marketing representative be contacted for assistance.
5. Holset “E or QE” Type Air Compressors - In order for the
AD-9™ air dryer to function properly when installed with
the Holset Type “E or QE” compressor, several
specialized Holset components are required. Consult
your local authorized Holset parts outlet or sales
representative for additional information.
6. Use of Standard or Extended Purge AD-9™ Air Dryer Use the following guidelines:
Total Vehicle Reservoir
Volume
Less than 9,000 cu. in. ..................Standard AD-9™ Air Dryer
Requirement
9,000 - 12,500 cu. in. ...........................Extended Purge AD-9™ Air
Dryer
Greater than 12,500 cu. in. ............Contact Bendix Rep. or
Bendix Engineering
LOCATING AD-9™ AIR DRYER ON VEHICLE
1. The AD-9™ air dryer must be mounted vertically (purge
exhaust toward road surface) outside the engine
compartment in an area of air flow while the vehicle is in
motion. The AD-9™ air dryer must not be exposed to
direct wheel splash (located behind axle mud flap is
acceptable).
2. Locate the AD-9™ air dryer as close to the first (supply)
reservoir as possible.
3. Do not locate the AD-9™ air dryer near heat producing
components such as the vehicle exhaust and make
certain adequate clearance from moving components
(e.g. drive shaft, suspension, pitman arm, etc.) is
provided.
4. Locate the AD-9™ air dryer on vehicle so that a minimum
of 1 1 inches (28 cm) clearance below the end cover is
available to allow servicing. Alternatively , provide access
to the bracket bolts so the unit may be removed for
servicing.
5. When choosing the mounting location for the AD-9™ air
dryer, note the discharge line length requirements stated
under the heading Connecting the Air Lines, elsewhere
in this instruction sheet.
Important Note: Under normal operating conditions, the
maximum inlet air temperature for the AD-9™ air dryer is
160 degrees Fahrenheit.
VEHICLE PREPARATION
1. Park the vehicle on a level surface and prevent movement
by means other than the brakes.
2. Drain all reservoirs to 0 p.s.i. (0 kPa).
LOWER
BRACKET
←
←←
←←
2-1/8"
←←
END
COVER
FIGURE 9 - LOWER BRACKET INSTALLATION
EXTRA
LONG
BRACKET
CAP SCREW
←←
←
SPECIAL
WASHER
MOUNTING THE AD-9™ AIR DRYER
1. To install the lower mounting bracket on the AD-9™ air
dryer, it will be necessary to remove and discard two of
the end cover bolts and lock nuts. To determine which
end cover bolts to utilize to attach the lower bracket,
take into consideration the piping connections required
to install the AD-9™ air dryer and use those that will best
SLEEVE NUT
MOUNTING
BRACKET STRAP
MOUNTING
BRACKET
SADDLE
Change Image
5/16" CAP
SCREW
FIGURE 10 - UPPER MOUNTING BRACKET AND STRAP
11
CONTROL
(HIDDEN)
UNLOADER
PORT
COMPRESSOR
CON
10 AMP - 12V
5 AMP - 24V
FUSE
FIGURE 11 - AD-9™ AIR DRYER CHARGE CYCLE
SUP
14 GA WIRE
TO IGNITION
& GROUND
DEL
position the unit for ease of installation. Locate the
bracket such that it cradles the end cover as shown in
Figure 9. Utilizing the two 2-3/8" long cap screws, lock
nuts and special washers provided with the AD-9™ air
dryer retrofit unit, attach the lower mounting bracket and
torque to 270-385 in. lbs.
2. Assemble the mounting strap and upper mounting
bracket as illustrated in Figure 10, by utilizing the 5/16"
cap screw (25) and sleeve nut (28).
3. Place the upper bracket assembly onto the shell of the
AD-9™ air dryer and orient it so that it bears entirely on
the cylindrical surface and does not extend onto the
domed top. The slot spacing between the upper and
lower bracket should be a minimum of 5.5 inches apart.
Do not tighten strap onto the shell at this time.
4. Mount the AD-9™ air dryer on the vehicle using 3/8" bolts
(grade 5 min.) and washers. Torque to 25 ft. Ibs. (300
inch pounds.) After positioning and mounting the upper
bracket assembly according to the installation
requirements, torque the 5/16" nut to 80-120 in. Ibs. to
tighten strap onto the shell.
GOVERNOR
SAFETY VALVE
SUPPLY
DELIVERY
RESERVOIR
#1
TO RESERVOIR
#2
CONNECTING THE AIR LINES
PURGE CONTROL LINE
1. Install a purge control air line having a minimum inside
diameter of 3/16 inches between the AD-9™ air dryer
end cover control port and an unused unloader port on
the governor. The control line must be plumbed direct to
the governor and not in series with automatic drain valves,
lubrication systems, etc.
2. The control line should slope downward to the end cover
without forming potential water traps.
DISCHARGE LINE
General:
Refer to Appendix A, Table A for recommended discharge
line lengths and sizes for various vehicle applications and
vocations.
PURGE EXHAUST LINE
1. If it is necessary to direct AD-9™ air dryer discharge
contaminants away from vehicle components it may be
necessary to purchase a special exhaust cover for the
AD-9™ air dryer (Pc. No. 5003838). A one inch (25.4
mm) I.D. hose can be clamped on the special AD-9™ air
dryer exhaust cover.
12
WIRING THE HEATER/THERMOSTAT
1. Determine the vehicle’s electrical system voltage and
™
make certain that the AD-9
air dryer that is to be
installed contains the same voltage heater. Use the
™
AD-9
air dryer part number to confirm the proper voltage.
™
The AD-9
air dryer is available with either a 12 or 24
volt heater which uses 75 watts of power .
2. A two lead, 12 inch, wire harness with attached weather
resistant connector is supplied with all retrofit and
replacement AD-9™ air dryers. Connect one of the two
leads of the wire harness to the engine kill or ignition
switch. The remaining lead of the wire harness must be
connected to a good vehicle ground (not to the air dryer
or its mounting bracket). A fuse should be installed in
the power carrying wire; install a 10 amp fuse for 12 volt
heaters and a 5 amp fuse for a 24 volt heater.
3. Use 14 GA wire if it is necessary to lengthen the wire
harness provided with the AD-9
™
air dryer. Make certain
all wire splices are waterproofed.
4. Tie wrap or support all electrical wire leading to the
AD-9™ air dryer at 6 - 8 inch intervals. Note: Wires should
have sufficient slack and not completely taught.
TESTING THE AD-9™ AIR DRYER
Before placing the vehicle in service, perform the following
tests:
1. Close all reservoir drain cocks.
2. Build up system pressure to governor cut-out and note
that the AD-9™ air dryer purges with an audible escape
of air.
3. “Fan” the service brakes to reduce system air pressure
to governor cut-in. Note that the system once again builds
to full pressure and is followed by a purge at the AD-9
air dryer exhaust.
4. It is recommended that the following items be tested for
leakage to assure that the AD-9™ air dryer will not cycle
excessively.
(A) Total air system leakage (See Bendix publication
BW-5057 “Air Brake Handbook”).
(B) Compressor unloader mechanism.
(C) Governor.
(D) Drain cock and safety valve in first (supply) reservoir.
(E) All air connections leading to and from the first
(supply) reservoir.
™
13
AD-9™ AIR DRYER TROUBLESHOOTING CHART
SYMPTOMS
1. Dryer is constantly
“cycling” or purging.
Dryer purges frequently
(every 4 minutes or less
while vehicle is idling).
CAUSE
A. Excessive system
leakage. IMPORT ANT:
Note whether air
pressure loss is shown
on dash gauge(s).
Pressure loss shown on
gauges is caused by
service brake system or
component leakage.
Pressure loss NOT
SHOWN on gauges is
caused by supply
system or component
leakage.
REMEDY
A. If leakage IS SHOWN on gauges test for
excessive service brake system leakage.
Allowable leakage:
Pre-121 vehicles, single vehicles - 2 psi/
minute.
Tractor trailer - 3 psi/minute.
121 vehicles, single vehicle - 1 psi/minute per
service reservoir.
Tractor trailer - 3 psi/minute per service
reservoir. Rep air and retest as required.
If leakage is NOT SHOWN on gauges test for
excessive supply system leakage.
Remove drain cock or valve in supply reservoir (wet
tank) and install air gauge. Build system pressure,
allow air dryer to purge and observe air gauge in
supply reservoir . Pressure drop should not exceed 1
psi per minute. Perform tests 1 to 6 in the order
presented.
14
AD-9™ AIR DRYER TROUBLESHOOTING CHART
SYMPTOMS CAUSE
REMEDY
1. Test fittings, hoses, lines and connections.
Apply soap solution to detect excessive
leakage. Tighten or replace as needed then
repeat the air dryer charge-purge cycle and
observe the gauge installed in the supply
reservoir . If leakage is within limits remove gauge
from reservoir and replace drain cock or valve. If
excessive leakage is detected, continue testing.
2. Test accessories connected to supply
reservoir. Drain all air pressure from system,
disconnect all air lines leading to accessories
(fan clutch, wipers, air seats, etc.) and plug the
reservoir at disconnection point. Build air system
pressure until air dryer purges and observe
supply reservoir gauge. If leakage is no longer
excessive, repair or replace leaking accessory . If
excessive leakage is detected, continue testing.
3. Test governor leakage. Build system pressure
to governor cut-out turn off engine and apply
soap solution to governor exhaust port and
around cap. Leakage should not exceed a 1"
bubble in 5 seconds. Reduce system pressure
to 80 psi or less, and reapply soap solution.
Leakage should not exceed a 1" bubble in 5
seconds. If excessive leakage is detected in
either test, repair or replace governor .
4. Test compressor unloader leakage. Drain all
air pressure from system and remove the
governor from the compressor . T emporarily plug
the governor unloader port or air line that mated
with, or connected to, the compressor. Build air
system pressure until air dryer purges then
IMMEDIA TEL Y SHUT OFF THE ENGINE.
Observe the air gauge in the supply reservoir . If
leakage is within limits, replace the compressor
unloaders. Reconnect the governor to the
compressor (after removing plug installed in
governor) and retest while observing supply
reservoir gauge. If excessive leakage is
detected, continue testing.
5. Test air dryer purge valve and outlet
(delivery) check valve. Drain all air pressure
from system, remove the control line connection
at the air dryer and plug the end of the air line
leading to the governor (not the air dryer control
port). Build system pressure to governor cut-out
and observe air gauge. If little or no pressure
drop is observed replace the air dryer check
valve. If pressure drop continues apply soap
15
AD-9™ AIR DRYER TROUBLESHOOTING CHART
SYMPTOMS CAUSE
B. Leaking purge valve
housing assembly and/or
o-rings in AD-9™ air dryer
end cover.
C. Holset “E” type
compressor .
REMEDY
solution to air dryer purge exhaust and purge
control port (where the control line was
removed). Leakage should not exceed a 1"
bubble in 5 seconds. If leakage is excessive
repair or replace purge valve assembly .
6. With gauge installed at RES port of governor,
pressure should not drop below “Cut-In” pressure
at the onset of the compressor “Unloaded”
cycle. If pressure drops, check for “kinks” or
restrictions in line connected to RES port. Line
connected to RES port on governor must be
same diameter, or preferably larger than, lines
connected to UNL port(s) on governor .
B. With the supply port open to atmosphere, apply
120 psi at the control port. Apply a soap solution
to the supply port and exhaust port (purge valve
seat area). Permissible leakage - 1" bubble in 5
seconds.
C. Test the Holset E Compressor unloader system
with feedback line and check valve for proper
operation. Make certain Holset ECON is not in
use with the drop-in version of the air dryer, if so,
remove and retest.
Check Valve
16
Feed Back Line
Typical Drop-In Air Dryer End Cover
When installing a Bendix Drop-In air dryer in a
system equipped with a Holset E or QE
compressor , remove the Holset ECON valve along
with its feed back and governor control line.
AD-9™ AIR DRYER TROUBLESHOOTING CHART
SYMPTOMS CAUSE
2. Water in vehicle
reservoir.
A. Desiccant requires
replacement - excessive
contaminants in
desiccant cartridge
assembly.
B. Improper discharge line
length or improper line
material. Maximum air
dryer inlet temperature is
exceeded.
C. Air system charged from
outside air source
(outside air not passing
through air dryer).
D. Air dryer not purging
(see Symptom #5).
E. Purge (air exhaust) time
insufficient due to
excessive system
leakage (see causes for
Symptom #1).
REMEDY
A. Replace desiccant cartridge.
B. Refer to section entitled “Connecting the Air
Lines” as well as Appendix A, Table A columns
1 & 2 then check line size and length.
C. If system must have outside air fill provision,
outside air should pass through air dryer. This
practice should be minimized.
D. See Symptom #5.
E. Check causes and remedies for Symptom #1.
F. Excessive air usage,
duty cycle too high - Air
dryer not compatible
with vehicle air system
requirement (Improper air
dryer/vehicle
application).
NOTE: Duty Cycle is the
ratio of time the compressor
spends building air to total
engine running time. Air
compressors are designed
to build air (run “loaded”) up
to 25% of the time. Higher
duty cycles cause
conditions that affect air
brake charging system
performance which may
require additional
maintenance. Factors that
add to the duty cycle are: air
suspension, additional air
accessories, use of an
undersized compressor,
frequent stops, excessive
leakage from fittings,
connections, lines,
chambers or valves, etc.
F . See Appendix A, Table A, column 1, for
recommended compressor sizes. If the
compressor is “too small” for the vehicle vocation
(for example, where a vehicle’s vocation has
changed or service conditions exceed the original
vehicle or engine OE spec’s) then upgrade the
compressor . Note: The costs incurred (e.g.
installing a larger capacity compressor , etc.) are
not covered under original compressor warranty .
Charge Cycle Time - The AD-9™ air dryer is
designed to provide clean, dry air for the brake
system. When a vehicle’s air system is used to
operate non-brake air accessories it is necessary
to determine that during normal, daily operation
the compressor should recover from governor
“cut-in” to governor “cut-out” (usually 100 psi to
120 psi) in 90 seconds or less at engine RPM’s
commensurate with the vehicle vocation. If the
recovery time consistently exceeds this limit, it
may be necessary to “bypass” the air accessory
responsible for the high air usage. An example of
where a by-pass system would be required is
when the compressor is used to pressurize a
tank trailer for purposes of off-loading product.
Consult your local authorized Bendix parts outlet
or sales representative for additional information.
17
AD-9™ AIR DRYER TROUBLESHOOTING CHART
SYMPTOMS CAUSE
G . Air compressor
discharge and/or air
dryer inlet temperature
too high.
REMEDY
Purge Cycle Time - During normal vehicle
operation, the air compressor must remain
unloaded for a minimum of 20 seconds for
the standard AD-9™ air dryer or 30 seconds
for the Extended Purge Model. These
minimum purge times are required to ensure
complete regeneration of the desiccant material.
If the purge time is consistently less than the
minimum, an accessory by-pass system must
be installed. Consult your local authorized Bendix
parts outlet or sales representative for additional
information.
European Air Brake Systems - Brake systems
that incorporate compressors without integral
unloading mechanisms and/or utilize a
compressor discharge line unloader valve have
special air dryer installation requirements.
Consult your local authorized Bendix parts outlet
or sales representative for additional information.
Air Compressor Size - Although the AD-9™ air
dryer can be used in conjunction with larger
compressors, it was designed primarily for units
rated for up to 17 CFM. It is recommended that
when using the AD-9™ air dryer with a
compressor which has a rated displacement
exceeding 17 CFM that an authorized Bendix
parts outlet or Bendix marketing representative
be contacted for assistance.
G. Restricted discharge line. See Appendix A,
T able A, column 1 & 2 for recommended sizes. If
discharge line is restricted or more than 1/16"
carbon build up is found, replace the discharge
line. Replace as necessary.
Discharge Line Freeze-Up. The discharge line
must maintain a constant slope down from the
compressor to the air dryer inlet fitting to avoid low
points where ice may form and block the flow. If,
instead, ice blockages occur at the air dryer inlet,
insulation may be added here, or if the inlet fitting is
a typical 90 degree fitting, it may be changed to a
straight or 45 degree fitting. For more information on
how to help prevent discharge line freeze-ups, see
Bendix Bulletins TCH-08-21 and TCH-08-22. Shorter
discharge line lengths or insulation may be required
in cold climates.
Insufficient coolant flow through compressor.
Inspect coolant line. Replace as necessary (I.D. is
1/2" min.). Inspect the coolant lines for kinks and
restrictions and fittings for restrictions. Replace as
necessary. V erify coolant lines go from engine block
to compressor and back to the water pump. Repair
as necessary.
18
AD-9™ AIR DRYER TROUBLESHOOTING CHART
SYMPTOMS CAUSE
H. Compressor malfunction.
REMEDY
Restricted air inlet (not enough air to
compressor). Check compressor air inlet line for
restrictions, brittleness, soft or sagging hose
conditions, etc. Repair as necessary. Inlet line size
is 3/4 ID. Maximum restriction requirement for
compressors is 25 inches of water. Check the
engine air filter and service if necessary (if possible,
check the air filter usage indicator).
Poorly filtered inlet air (poor air quality to
compressor). Check for leaking, damaged or
malfunctioning compressor air inlet components
(e.g. induction line, fittings, gaskets, filter bodies,
etc.). Repair inlet components as needed. Note:
Dirt ingestion will damage compressor and is not
covered under warranty.
If you found excessive oil present in the service
reservoir and you did not find any issues above, the
compressor may be passing oil.
Replace compressor. If still under warranty, follow
normal warranty process.
H. If you found excessive oil present in the service
reservoir and you did not find any issues above,
the compressor may be passing oil. Test the
compressor using the BASIC cup method as
described in the Bendix compressor service
manual and referred to in Appendix A, Table A,
column 5.
Replace compressor. If still under warranty, follow
normal warranty process.
I. Air by-passes desiccant
cartridge assembly .
I. If vehicle uses Holset compressor, inspect
feedback check valve for proper installation and
operation.
When replacing the desiccant cartridge, make sure
desiccant cartridge assembly is properly installed
and sealing rings are in place on mounting surface
of desiccant cartridge.
Check Valve
Feed Back Line
Typical Drop-In Air Dryer End Cover
19
AD-9™ AIR DRYER TROUBLESHOOTING CHART
SYMPTOMS CAUSE
3. Oil present at air dryer
purge exhaust or
cartridge during
maintenance.
4. Safety valve on air dryer
“popping off” or
exhausting air.
J. Desiccant requires
replacement.
A. Air brake charging
system is functioning
normally.
A. Restriction between air
dryer and supply (first)
reservoir.
B. Air dryer safety valve
malfunction.
REMEDY
J. Replace desiccant cartridge assembly. Refer to
Appendix A, Table A columns 3 & 4 for
recommended intervals.
A. Air dryers remove water and oil from the air
brake charging system. A small amount of oil is
normal. Check that regular maintenance is being
performed and that the amount of oil in the air
tanks (reservoirs) is within the acceptable range
shown on the BASIC cup (see also column 5 of
Appendix A, Table A.) Replace the air dryer
cartridge as needed and return the vehicle to
service.
A. Check to determine if air is reaching supply
reservoir. Inspect for kinked tubing or hose.
Check for undrilled or restricted hose or tubing
fittings and repair or replace as needed.
B. Verify relief pressure is at vehicle or component
manufacturer specifications. Replace if
malfunctioning.
5. Constant exhaust of air
at air dryer purge valve
exhaust. (Charge
mode.)
C. Desiccant cartridge
maintenance required.
D. Malfunctioning defective
discharge check valve in
end cover of the AD-9
™
air dryer.
E. Excessive pressure
pulsations from
compressor. (Typical
single cylinder type).
F. Governor malfunction.
Missing or restricted
governor control line
installation.
A. Air dryer purge valve
leaking excessively.
B. Compressor fails to
unload (stop
compressing air) and air
dryer purge exhaust
makes “sputtering” or
“popping” sound.
C. Refer to Appendix A Table A and column 3.
Check compressor for excessive oil passing
and/or correct compressor installation. Repair or
replace as necessary. Replace desiccant
cartridge.
D. Test to determine if air is passing through check
valve. Repair or replace.
E. Increase volume in discharge line by increasing
length or diameter. Add a ping tank (small
reservoir).
F. Test governor operation and/or inspect the
control line leading from the governor UNL
(unloader) port to the air dryer control port.
A. With compressor loaded, apply soap solution on
purge valve exhaust, to test for excessive
leakage. Repair purge valve as necessary.
B. Confirm failure to unload by increasing &
decreasing engine RPM and noting change in
the rate of leakage and intensity of
accompanying leakage sound. Repair/replace
compressor unloaders.
20
AD-9™ AIR DRYER TROUBLESHOOTING CHART (Continued)
SYMPTOMS CAUSE
6. Can not build system
air pressure.
7. Air dryer does not purge
or exhaust air .
8. Desiccant material
being expelled from air
dryer purge valve
exhaust (may look like
whitish liquid or paste
or small beads.)
- OR -
Unsatisfactory
desiccant life.
C. Purge control line
connected to reservoir or
exhaust port of governor .
D. Purge valve frozen open -
malfunctioning heater
and thermostat, wiring,
blown fuse.
E. Excessive system
leakage.
F . Purge valve stays open -
supply air leaks to
control side.
A. Inlet and outlet air
connections reversed.
B. Check valve between air
dryer and first reservoir .
C. Kinked or blocked
(plugged) discharge line.
D. Excessive bends in
discharge line (water
collects and freezes).
E. Refer to Symptom 4,
Causes E & F.
A. Missing, broken, kinked,
frozen, plugged or
disconnected purge
control line.
B. Faulty air dryer purge
valve.
C. See Causes B, E, G for
Symptom #4.
A. This symptom is almost
always accompanied by
one or more of
Symptoms 1, 2, 3, 4 and
5. See related causes for
these Symptoms above.
B. Air dryer not securely
mounted. (Excessive
vibration.)
C. Malfunctioning or
saturated desiccant
cartridge.
D. Compressor passing
excessive oil.
REMEDY
C. Purge control line must be connected to
unloader port of governor.
D. Test heater and thermostat as described in
Preventative Maintenance Section.
E. See Symptom #1.
F . Repair purge valve and housing.
A. Connect compressor discharge to air dryer
supply port. Reconnect lines properly .
B. Test check valve for proper operation. Rep air or
replace as necessary .
C. Check to determine if air passes through
discharge line. Check for kinks, bends,
excessive carbon deposits, or ice blockage.
D. Discharge line should be constantly sloping from
compressor to air dryer with as few bends as
possible.
E. Refer to Symptom #4, Remedies E & F .
A. Inspect control line from governor UNL (unloader)
port to control port of air dryer. Test to determine
air flows through purge control line when
compressor unloaded. Check for undrilled
fittings. (See Symptom #4, Remedy C.)
B. After determining air reaches purge valve
(Remedy A above), repair purge valve.
C. See Causes, B, E, G for Symptom #4.
A. See Causes and Remedies for Symptoms 1, 2,
3, 4 and 5.
B. Vibration should be held to minimum. Ad d
bracket supports or change air dryer mounting
location if necessary .
C. Replace desiccant cartridge assembly.
D. Check for proper compressor installation; if
symptoms persist, replace compressor.
21
AD-9™ AIR DRYER TROUBLESHOOTING CHART (Continued)
SYMPTOMS CAUSE
9. “Pinging” noise
excessive during
compressor loaded
cycle.
10.Constant seepage of air
at air dryer purge valve
exhaust (non-charging
mode.)
1 1. The air dryer purge
piston cycles rapidly in
the compressor
unloaded (noncompressing) mode.
E. Desiccant cartridge not
assembled properly to
end cover. (Loose
attachment)
A. Defective check valve
assembly in AD-9™ air
dryer end cover.
B. Leaking Turbo Cutoff
valve.
C. Leaking purge valve
control piston o-ring.
A. Defective check valve
assembly in AD-9
™
air
dryer end cover.
B. Leaking Turbo Cutoff
valve.
C. Leaking purge valve
control piston o-ring.
A. Compressor fails to
“unload”.
REMEDY
E. Check the torque on the desiccant cartridge to
end cover attachment. Refer to assembly
section of this service data sheet.
A. Refer to Remedy C, Symptom #1.
B. Repair or replace purge valve assembly.
C. Repair or replace purge valve assembly .
A. Refer to Remedy C, Symptom #1.
B. Repair or replace purge valve assembly.
C. Repair or replace purge valve assembly .
A. Faulty governor installation; no air line from
governor to compressor or line is kinked or
restricted. Install or repair air line.
22
Appendix A
Table A: Maintenance Schedule and Usage Guidelines
Regularly scheduled maintenance is the single most important factor in maintaining the air brake charging system.
Vehicle Used for:
Low Air Use
Compressor with less than 15% duty
cycle
e.g. Line haul single trailer
w/o air suspension, air over
hydraulic brakes.
Compressor with up to 25% duty cycle
e.g. Line haul single trailer
with air suspension,
school bus.
High Air Use
Compressor with up to 25% duty cycle
e.g. Double/triple trailer, open
highway coach/RV, (most)
pick-up & delivery, yard or
terminal jockey, off-highway,
construction, loggers, concrete
mixer, dump truck, fire truck.
Compressor with up to 25% duty cycle
e.g. City transit bus, refuse,
bulk unloaders, low boys,
urban region coach, central
tire inflation.
Column 1
Typical Discharge mended mended Reservoir
Compressors Line Air Dryer Reservoir Oil Contents
No. of Spec'd Cartridge Drain at Regular
Axles Replacement1Schedule2Drain Interval
5
or
less
5
or
550 air compressor
®
less
Tu-Flo
®
air compressor
®
Bendix
BA-921
®
Bendix
8
or
less
750 air compressor
®
Tu-Flo
®
Bendix
air compressor
596
™
12
or
, or DuraFlo
®
less
BA-922
®
Column 2 Column 3 Column 4 Column 5
Recom- Recom- Acceptable
I.D.
1/2 in.
For oil carry-over
control
5/8 in. 9 ft.
For oil carry-over
control
Length
4
suggested
upgrades:
9 ft.1/2 in.
4
suggested
upgrades:
6 ft.
Every 3
Years
Recom-
mended
Every
Month -
Max of every
90 days
5/8 in. 12 ft.
1/2 in.
12 ft.
Every 2
For oil carry-over
4
control
suggested
upgrades:
Years
5/8 in. 15 ft.
Every
Month
5/8 in.
12 ft.
Every
For oil carry-over
4
control
suggested
upgrades:
Y ear
3/4 in. 15 ft.
BASIC test
acceptable
range:
3 oil units
per month.
See
appendix
A.
For the
BASIC
Test Kit:
Order
Bendix
P/N
5013711
BASIC test
acceptable
range:
5 oil units
per month.
See
appendix
A.
3
Bendix
Footnotes:
1 With increased air demand the air dryer cartridge needs to be replaced more often.
2 Use the drain valves to slowly drain all reservoirs to zero psi.
3 Allow the oil/water mixture to fully settle before measuring oil quantity.
4 To counter above normal temperatures at the air dryer inlet, (and resultant oil-vapor passing
upstream in the air system) replace the discharge line with one of a larger diameter and/or longer
length. This helps reduce the air's temperature. If sufficient cooling occurs, the oil-vapor condenses
and can be removed by the air dryer. Discharge line upgrades are not covered under warranty.
Note: To help prevent discharge line freeze-ups, shorter discharge line lengths or insulation may be
required in cold climates. (See Bendix Bulletins TCH-08-21 and TCH-08-22.)
5 For certain vehicles/applications, where turbo-charged inlet air is used, a smaller size compressor
may be permissible.
Note: Compressor and/or air dryer
upgrades are recommended in cases
where duty cycle is greater than the
normal range (for the examples above).
For Bendix
compressors, unloader service is
recommended every 250,000 miles.
®
Tu-Flo® 550 and 750
23
Appendix B
Additional Troubleshooting Information
The troubleshooting procedure presented on the following pages has been excerpted from a troubleshooting card entitled:
Troubleshooting Charging and Air Supply Systems. The complete card can be obtained from authorized Bendix parts
outlets under literature number BW1779. It is presented here because of the air dryers connection to the supply air system
and for convenience. The procedure is not all inclusive but rather represents the most commonly encountered complaints.
CONVENTIONAL
SUPPLY SYSTEM
& INTEGRAL PURGE
AIR DRYER
HOLSET TYPE
"E & QE"
COMPRESSOR
WITH ECON
VAL VE
“E OR QE”
COMPRESSOR
TWO CYL.
COMPRESSOR
HOLSET
HOLSET
ECON VALVE
AIR DRYER
GOVERNOR
("CHOKE" IN INLET)
GOVERNOR
SAFETY
VALVE
STANDARD SINGLE
CHECK VALVE
DRYER
SPECIAL
SINGLE CHECK
STANDARD SINGLE CHECK VALVE
(USED W/INTEGRAL PURGE AIR
DRYERS)
SUPPLY
SAFETY
VALVE
AIR
SUPPLY
STANDARD SINGLE
CHECK VALVE
REAR
FRONT
REAR
FRONT
LOW PRESSURE
INDICATOR
DASH
GAUGE
DASH
GAUGE
LOW
PRESSURE
INDICATOR
DRAIN COCK
HOLSET TYPE
"E & QE"
COMPRESSOR
W/O ECON
VALVE
24
HOLSET
“E OR QE”
COMPRESSOR
BW1627 © 2007 Bendix Commercial Vehicle Systems LLC • All Rights Reserved • 6/2007 • Printed in U.S.A.
GOVERNOR
SPECIAL
SINGLE CHECK
("CHOKE" IN INLET)
SAFETY
VALVE
AIR DRYER
SUPPLY
SINGLE CHECK -
PROTECTION VALVE
(USED W/SYSTEM
PURGE AIR DRYERS)
LOW PRESSURE
INDICATOR
REAR
FRONT
SINGLE CHECK VALVE (USED
W/INTEGRAL PURGE AIR DRYERS)
DASH
GAUGE
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