Truck Vin H72526 cummins ism air compressor part number..

Have you checked to see if your getting the proper signal from the gov to the unloader at the compressor to signal it off? Depending what type of dryer you have on your truck, it may be a positive purge and start the regeneration process to leak off and get rid of the moisture. What I usually do is I have a T-fitting made up to tie into the discharge line at the dryer and run a hose and pressure gauge to it. Then when you are running the engine you can see the output of the compressor when the gov is trying to kick it off. If you are getting the signal from the gov to shut off the compressor but the pressure it still raising them the compressor is at fault. Once the comp kicks off you should actually see the pressure start to decrease because of the one way check valve in the wet tank. While I am running the engine Ill have the unloader valve line off at the compressor and as soon as it starts putting air out I push it back in and watch my gauge.

These compressors are known for the unloaders getting carboned up inside also. We have just developed ways like above to ty and isolate the issue.

Let me see what I can come up with for that.

Air Dryer

Wabco System Saver 1200 Series

The dryer incorporates valves for both types of compressors used. Desiccant is contained in a disposable cartridge that is screwed onto the valve housing.

Note: The Air Dryer Wabco System Saver 1200 Series P does not have a Regeneration Valve to cool air intake. The System Saver relies on the Purge Tank to perform this function.

Warning

Do not disassemble the cartridge. No replacement parts are available and the cartridge contains a spring under pressure which can not be mechanically caged. The sudden release of the spring could cause it to be ejected violently, causing serious personal injury.

1200 Series Wabco Air Dryer

Wabco 1200P Wabco Air Dryer

Charge Cycle

During system pressure build-up, compressed air passes into the air dryer where the coalescent filter removes contaminants and the air is further cooled at the outer walls of the cartridge. Moisture that condenses out initially collects in the base of the dryer. The moisture laden air then flows through the desiccant from the top to the bottom and becomes progressively dryer as water vapor is adsorbed.

Dry air exits at the bottom of the cartridge and flows through the check valve and then exits out to the wet tank.

Purge Cycle

When the compressor unloads, the purge valve opens allowing the initial decompression of the dryer (purge) and expels the water collected in the base of the dryer. The volume of air held in the purge tank back flows through the dessicant. This flow cleans and dries the dessicant preparing it for the next cycle. The air held in the purge tank. is the cleanest air from the completed pumping cycle. This provides a more efficient regeneration (purge) cycle.

Air Dryer Wabco System Saver 1200 Series

1. Regeneration Valve for the Wabco Air Dryer 1200, 1200E Series

   Note: The Wabco Air Dryer 1200P Series does not use the Regeneration Valve

Wabco System Saver Twin Series

The twin air dryer cartridges contain dessicant material that filters and dries compressed air. The process begins when the supply tank pressure drops below cut-in pressure (approximately 7 bar (100 psi)). When this occurs, the governor turns the compressor on. The compressor sends air to the supply port of the dryer, and an air drying cycle begins.

1. Pressure Relief Valve

Charge Cycle

When the air drying cycle begins, air enters the dryer at the supply port. Air flows past the piston in to the first (right) cartridge. Air then flows through the cartridge where it is dried; moisture and contaminants are filtered our through the dessicant material in the cartridge. Dry, clean air flows to the delivery port of the dryer for delivery to the supply tank.

Note: Some air is diverted to the second cartridge where it moves upward through the dessicant. This cleans and dries (regenerates) the dessicant.

1. Dryer Inlet
2. Dryer Outlet
3. Governor Port
4. Purge Valve

While the compressor is running, a mild flow of air vents to the atmosphere through the purge valve. Switching in the compressor's is controlled by a timer/solenoid. The pistons shift from right to left, reversing the airflow pattern.

1. Dryer Inlet
2. Dryer Outlet
3. Governor Port
4. Purge Valve

As the air drying cycle continues cartridge functions are reversed. Incoming air enters the second (left) cartridge for drying and then flows to the delivery port. A small amount of dried air flows into the first (right) cartridge to regenerate dessicant. Alternating air drying cycles continue, one cartridge to the other, every 60 seconds as long as the compressor is running

1. Dryer Inlet
2. Dryer Outlet
3. Governor Port
4. Purge Valve

Purge Cycle

The supply tank reaches cutout pressure and then the governor unloads the compressor. The governor supplies air to the unloader port of the dryer. Moisture and contaminants pass through the purge valve and out of dryer.

A burst of air occurs when the dryer purges; airflow from purge valve ceases for the duration of the unloaded cycle.

1. Dryer Inlet
2. Dryer Outlet
3. Governor Port
4. Purge Valve

Wabco System Saver Twin Series

1. Left Piston Kit
2. Orifice Kit
3. Dessicant Cartridge
4. Air Dryer Base
5. Right Piston Kit
6. Right Piston Cover Kit
7. Solenoid & Armature Parts (3 Kits)
8. Charging Valve Kit
9. Purge Valve Kit
10. Outlet Check Valve Kit
11. Heater Kit
12. Left Piston Cover Kit
13. Manufacturing Location Code
14. Part Number
15. Date Code-First two digits=Build Week/Last two digits=Build Year

Wabco System Saver Twin Series Routing

1. Compressor
2. Governor
3. Compressor Intake Line
4. Unloader Port
5. System Saver Twin Air Dryer
6. Dryer Outlet
7. Check Valve
8. System Reservoir
9. To Brake System
10. Supply Tank
11. Dryer Inlet
12. Compressor Discharge Line
13. Governor Port

Bendix AD-IP

This dryer is used in two configurations where one is used exclusively for the Holset compressor. Because of the need for the Holset to have the discharge line fully pressurized also during the unloaded mode, the dryer for the Holset compressor has a check valve arrangement that ties the wet tank pressure into the discharge line during the air dryer purge cycle.

Warning

Do not disassemble cartridge. No replacement parts are available and the cartridge contains a spring under pressure which can not be mechanically caged. The sudden release of the spring could cause it to be ejected violently, causing serious personal injury.

Charge Cycle

During compressor loading, air flows into the supply connection of the housing changing direction several times, thereby reducing the temperature, causing contaminants to condense and drop to the bottom toward the purge valve.

After exiting the housing, air flows into the cartridge. A coalescent filter, located between the outer and inner shells, separates heavier contaminants. Air, along with remaining water vapor, is further cooled as it continues to flow through the desiccant from the top to the bottom and becomes progressively dryer as water vapor is adsorbed.

Dry air exits at the bottom of the cartridge and flows through the check valve and then exits the discharge connection for the wet tank. Dry air also flows through the purge orifice to fill up the purge volume storage.

Purge Cycle

Regeneration of the desiccant takes place during the time it takes for the purge volume to slowly flow back through the purge orifice and into the desiccant bed. There it removes water vapor collected by the desiccant. The regeneration takes approximately 30 seconds.

Bendix AD–IP

AD-9 Air Dryer Design

AD-9 Air Dryer — Standard

Note: The Engine Turbo associated with the AD-9 Air Dryer is available with the Cummins Engine only.

The AD-9 air dryer collects and removes 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.

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 capscrews 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 turbocharger cutoff feature that is designed to prevent loss of engine turbo boost pressure during the purge cycle of the AD-9 air dryer. For easy service, the desiccant cartridge and discharge check valve assembly are screwed in. 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. Servicing the screw-in desiccant cartridge requires removal of the air dryer assembly from the vehicle.

The AD-9 has three female pipe thread air connections and each is identified as follows:

Port ID

Function/connection

4 — CON

Control port (purge valve control and turbo cutoff)

11 — SUP

Supply port (air in)

2 — DEL

Delivery port (air out)

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

AD-9 Charge Cycle

Note: The Engine Turbo associated with the AD-9 Air Dryer is available with the Cummins Engine only.

When the compressor is loaded (compressing air) compressed air, oil, oil vapor, water and water vapor flow 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 and 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, oil vapor and solid contaminants. Next, the air exits the oil separator and enters the desiccant drying bed. Air flowing through the column of desiccant becomes progressively dryer 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

AD-9 Purge Cycle

Note: The Engine Turbo associated with the AD-9 Air Dryer is available with the Cummins Engine only.

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 the line connecting the governor unloader port to the AD-9 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. 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. Air flowing from the desiccant drying bed to the open purge valve removes oil and solid contaminants collected by the oil separator.

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 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 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. After 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 Cutoff

The turbo cutoff valve prevents loss of engine turbocharger air pressure through the AD-9 in systems where the compressor intake is connected to the engine turbocharger. The turbo cutoff 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.

At the onset of the purge cycle, the downward travel of the purge piston is stopped when the turbo cutoff valve (tapered portion of the purge piston) contacts its mating metal seat in the purge valve housing. With the turbo cutoff valve seated (closed position), air in the discharge line and AD-9 inlet port is restricted from entering the air dryer. While the turbo cutoff effectively prevents loss of turbocharger boost pressure to the engine, some seepage of air may be detected under certain conditions of compressor engine and turbocharger operation. However, there will always be low pressure trapped in the discharge line.

AD-9 Turbo Cutoff

CR Turbo–2000

The dryer incorporates valves for both types of compressors used. A separate purge tank is used as there is no internal purge air storage. Desiccant is contained in a disposable cartridge that is screwed onto the valve housing.

Warning

Do not disassemble cartridge. No replacement parts are available and the cartridge contains a spring under pressure which can not be mechanically caged. The sudden release of the spring could cause it to be ejected violently, causing serious personal injury.

Charge Cycle

During compressor loading, air flows into the supply connection of the valve housing where it expands and is cooled. This causes oil and water vapor to condense and fall to the bottom.

After exiting the valve housing, air flows into the cartridge. A coalescent filter, located between the outer and the inner shells, separates heavier contaminants. Air, along with remaining water vapor, is further cooled as it continues to flow upward between the outer and inner shells. It then flows through the desiccant from the top to the bottom and becomes progressively dryer as water vapor is adsorbed.

Dry air exits the bottom of the cartridge, flows through the check valve and then exits the discharge connection onto the wet tank. Dry air also flows through the purge valve or orifice to fill the purge tank.

Purge Cycle

As air pressure reaches the cut out setting of the governor, the compressor unloads and the purge cycle of the dryer begins: The governor sends air to the control connection, thereby closing the turbo valve which closes off the air supply from the compressor. At the same time, the purge valve opens to atmosphere and expels separated contaminants in the initial air pressure release. Air is also flowing from the wet tank back to pressurize the supply line via a check valve.

Regeneration of the desiccant takes place during the time it takes for the purge volume to slowly flow back through the purge orifice and into the desiccant bed. There it removes the water vapor collected in the desiccant. The regeneration takes less than a minute.

Midland Pure Air Plus

A separate, replaceable coalescent filter is used for separating out large particles. This should be changed every 12 months regardless of desiccant cartridge exchange. Desiccant is contained in a disposable cartridge that is screwed on to the valve housing.

Note: Midland Pure Air Plus air dryers are not available with Holset compressors.

Warning

Do not disassemble the cartridge. No replacement parts are available and the cartridge contains a spring under pressure which can not be mechanically caged. The sudden release of the spring could cause it to be ejected violently, causing serious personal injury.

Charge Cycle

During compressor loading, air flows into the supply connection of the valve housing where it expands and is cooled. This causes oil and water vapor to condense and fall to the bottom.

After exiting the valve housing, air flows through the coalescent filter where heavier contaminants are separated. Air, along with remaining water vapor, is further cooled as it moves up into the cartridge. It then flows through the desiccant from the top to the bottom and becomes progressively dryer as water vapor is adsorbed. Dry air exits the bottom of the cartridge and flows through the check valve and then exits the delivery connection on the wet tank. Dry air also flows through the purge valve or orifice to fill up the purge tank.

Purge Cycle

As air pressure reaches the cut out setting of the governor, the compressor unloads and the purge cycle of the air dryer begins: The governor sends air to the control connection, thereby closing the turbo valve which closes off the air supply from the compressor. At the same time, the purge valve opens to the atmosphere.

Air Dryer Troubleshooting

SymptomCauseRemedy

Dryer is constantly cycling or purging.

• Excessive fluid in reservoirs.
• Governor faulty.
• Excessive system leakage.

• Drain reservoirs.
• Replace governor.
• Check for leaks in unloader valves, reservoirs, tubing, fittings, air dryer and drain valve.

Air leaks from exhaust port during pressure build-up.

• Purge valve worn.
• Dirt stuck in purge valve.
• Frozen purge valve.
• Governor faulty.
• Control air lines connected to the wrong port.

• Clean or replace valve.
• Clean or replace valve.
• Check heater.
• Replace governor.
• Check connections against air line schematic.

Air dryer does not unload when the compressor unloads.

• Purge valve is worn, stuck closed or is frozen shut.
• Tubing between governor and air dryer leaking, damaged or kinked.

• Clean or replace purge valve. Check heater.
• Repair or replace the air tubing.

Purge cycle is too long (more than 30 to 40 seconds).

• Purge valve stuck open.
• Turbo valve is leaking.
• Outlet valve stuck open.

• Replace valve.
• Replace valve.
• Replace valve.

Excessive amounts of water in air reservoirs.

• Desiccant saturated.
• Insufficient purge time due to leaks in the air system.
• Excessive temperature of air going into air dryer.
• Air dryer not purging.

• Replace desiccant cartridge.
• Check for leaks in supply system or in accessories.
• Compressor runs hot (inlet air to dryer maximum 65°C [150°F]).
• Check purge valve. Check tubing from air dryer to the governor; WABCO: Tubing between wet tank and air dryer kinked or blocked.

SymptomCauseRemedy

Safety valve opens (if equipped).

• Output valve blocked.
• Tubing blocked downstream from air dryer.
• Safety valve faulty.
• Desiccant cartridge plugged.
• Governor faulty so compressor overcharges.

• Clean or replace valve.
• Check for blockage, kinks or faulty components.
• Replace valve.
• Replace desiccant cartridge.
• Replace governor.

Air dryer valves freeze up.

• Heater or thermostat inoperative.

• Check fuse. Check for defective wiring, heater element or thermostat.