Bendix AD-9 User Manual

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

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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).

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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

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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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ORIFICE

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PURGE

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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.

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UPPER

BRACKET

STRAP

UPPER

BRACKET

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TURBO

CUTOFF

PISTON

FIGURE 4 - AD-9™ AIR DRYER TURBO CUTOFF

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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

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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

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.

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AD-9

AIR DRYER

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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

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air dryer.

AD-9

FIGURE 6 - HEA TER AND THERMOSTAT CONNECTOR

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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.

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

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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.

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 .

END

COVER

5 14 10

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

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.

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