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BENDIX AD-9 AIR DRYER - User Manual

BENDIX AD-9 AIR DRYER
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1
CONTROL
PORT
SUPPLY
PORT
SD-08-2412
Bendix
®
AD-9
Air Dryer
EXTENDED PURGE AD-9
AIR DRYER STANDARD AD-9
AIR DRYER
OUTER
SHELL
WIRING HARNESS
CONNECTION
DELIVERY PORT
DESCRIPTION
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 11 ............. Supply Port (air in).
DEL 2 ............... Delivery Port (air out).
OUTER
SHELL
SUPPLY
PORT
WIRING HARNESS
CONNECTION
DELIVERY PORT
CHECK
VALVE
ASSEMBLY
END COVER
CHECK
VALVE
ASSEMBLY
END COVER
CONTROL
PORT
FIGURE 1 - AD-9
AIR DRYER MODELS

Questions and Answers

  • R
    rowejeromeAug 1, 2025
    How to fix constant exhaust of air at the purge valve of my BENDIX Dehumidifier?
    • S
      scottdawnAug 1, 2025
      If there's a constant exhaust of air at the air dryer purge valve exhaust of your BENDIX Dehumidifier (charge mode), here's what you can check: * The air dryer purge valve may be leaking excessively. Apply a soap solution to the purge valve exhaust to test for leakage and repair as needed. * The compressor might fail to unload, causing a sputtering or popping sound. Confirm this by varying the engine RPM and noting changes in the leakage rate and sound. Repair or replace the compressor unloaders.
  • T
    Tiffany WilliamsAug 13, 2025
    Why can't my BENDIX Dehumidifier build system air pressure?
    • V
      Veronica RojasAug 13, 2025
      If your BENDIX Dehumidifier can't build system air pressure, consider these potential causes: * The inlet and outlet air connections might be reversed; connect the compressor discharge to the air dryer supply port correctly. * The check valve between the air dryer and the first reservoir might be faulty; test and repair or replace it as necessary. * The discharge line could be kinked or blocked; check for any obstructions, bends, carbon deposits, or ice blockage. * Excessive bends in the discharge line can cause water to collect and freeze; ensure the line slopes from the compressor to the air dryer with minimal bends.
  • M
    Michele MillerAug 19, 2025
    Why is my BENDIX Dehumidifier constantly cycling or purging?
    • L
      Lawrence LongAug 19, 2025
      Your BENDIX Dehumidifier might be constantly cycling or purging due to excessive system leakage. If gauges show leakage, test for excessive service brake system leakage, repair, and retest as needed. If leakage isn't shown on gauges, test for excessive supply system leakage by installing an air gauge in the supply reservoir and observing the pressure drop, which should not exceed 1 psi per minute. Perform tests 1 to 6 in the order presented.
  • C
    christina04Oct 25, 2025
    What to do if there is water in the vehicle reservoir of my BENDIX Dehumidifier?
    • G
      George GonzalezOct 25, 2025
      If you find water in the vehicle reservoir of your BENDIX Dehumidifier, consider the following possibilities: * The desiccant cartridge may need replacement due to excessive contaminants. * The discharge line might be of improper length or material, or the air dryer inlet temperature may be exceeded. Check the air line connections, size, and length. * The air system may be charged from an outside air source not passing through the air dryer; outside air should pass through the air dryer if this provision is necessary. * The air dryer might not be purging; refer to Symptom #5. * Insufficient purge time could be due to excessive system leakage; check the causes and remedies for Symptom #1. * Excessive air usage or an incompatible air dryer could be the issue; see Appendix A, Tab...
  • J
    Jennifer PerryNov 6, 2025
    Why is the safety valve on my BENDIX Dehumidifier popping off?
    • L
      lauren27Nov 6, 2025
      The safety valve on your BENDIX Dehumidifier might be popping off due to several reasons: * There could be a restriction between the air dryer and the supply reservoir. Check for kinked tubing or restricted fittings. * The air dryer safety valve itself may be malfunctioning and needs replacement after verifying the relief pressure against the manufacturer's specifications. * The desiccant cartridge might require maintenance; refer to Appendix A Table A and column 3 to check the compressor for excessive oil or correct installation. Replace the desiccant cartridge if needed. * A defective discharge check valve in the end cover of the AD-9™ air dryer might be malfunctioning. Test it and repair or replace it. * Excessive pressure pulsations from the compressor can also cause this i...

Summary

DESCRIPTION OF THE AD-9 TM AIR DRYER

OPERATION OF THE AD-9 TM AIR DRYER

CHARGE CYCLE

Describes the air drying process when the compressor is loaded.

PURGE CYCLE

Details the air drying process when the compressor unloads.

TURBO CUT-OFF FEATURE

PREVENTIVE MAINTENANCE

OPERATION & LEAKAGE TESTS

GENERAL SAFETY GUIDELINES

ASSEMBLY AND DISASSEMBLY

PURGE VALVE ASSEMBLY PROCEDURES

Instructions for assembling and disassembling the purge valve.

CLEANING & INSPECTION

INSTALLATION AND RETROFITTING

VEHICLE APPLICATION REQUIREMENTS

Outlines requirements for installing the dryer on various vehicles.

LOCATING AD-9 TM AIR DRYER ON VEHICLE

MOUNTING THE AD-9 TM AIR DRYER

AIR LINES CONNECTION AND WIRING

PURGE CONTROL LINE CONNECTION

Details on how to connect the purge control air line.

TESTING THE AD-9 TM AIR DRYER

AD-9 TM AIR DRYER TROUBLESHOOTING

TROUBLESHOOTING: CONSTANT DRYER CYCLING

Addresses frequent dryer cycling or purging issues and their causes.

TROUBLESHOOTING: WATER IN VEHICLE RESERVOIR

Diagnosing and resolving water accumulation in the vehicle reservoir.

TROUBLESHOOTING: INABILITY TO BUILD SYSTEM AIR PRESSURE

Guides on resolving issues preventing the air system from building pressure.

APPENDIX A: MAINTENANCE SCHEDULE

APPENDIX B: ADDITIONAL TROUBLESHOOTING

APPENDIX B: COMPRESSOR CONFIGURATIONS

Information on different compressor types and their diagrams.

BENDIX AD-9 AIR DRYER Specifications

General IconGeneral
TypeAir Dryer
ModelAD-9
ManufacturerBendix
Maximum Operating Pressure150 PSI
Inlet Port1/2" NPT
Outlet Port1/2" NPT
Reservoir VolumeNot Applicable
FunctionRemoves moisture and contaminants from compressed air

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