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Appendix V — Temporary Air Dryer Bypass 

46

Meritor WABCO

 Maintenance Manual 34 (Revised 03-16)

8 Appendix V — Temporary Air Dryer Bypass

Hazard Alert Messages

Read and observe all Warning and Caution hazard alert messages in 
this publication. They provide information that can help prevent 
serious personal injury, damage to components, or both.

WARNING

To prevent serious eye injury, always wear eye protection 
when you perform vehicle maintenance or service.

Park the vehicle on a level surface. Block the wheels to 
prevent the vehicle from moving. Support the vehicle with 
safety stands. Do not work under a vehicle supported only by 
jacks. Jacks can slip and fall over. Serious personal injury and 
damage to components can result.

Open drain valves on all reservoirs to remove all pressurized 
air from the air system before you disconnect any component. 
Pressurized air can cause serious personal injury.

Bypass Procedure

If the air dryer were to malfunction in a way that the air compressor 
cannot build up pressure within the system and the air dryer cannot 
be immediately repaired, a temporary bypass of the air dryer may be 
required. The bypass is a short term remedy only until the vehicle 
can make it to a repair facility and either have the air dryer repaired 
or replaced. Long term use of the vehicle with the air dryer 
bypassed could result in excessive moisture build up in the air 
system.

1.

Wear safe eye protection.

2.

Park the vehicle on a level surface. Block the wheels to prevent 
the vehicle from moving.

3.

Drain the entire air system. Open all of the drain valves on all of 
the reservoirs.

4.

Ensure that all residual pressure has been released and the air 
dryer has been drained to 0 psi. Then, remove the air supply 
line from the compressor to the inlet port.

5.

Remove the air line from the dryer discharge port.

6.

Install a T-fitting into the discharge port. Figure 8.1.

Figure 8.1

7.

Using the original fittings, reinstall the discharge line in one of 
the branches of the T-fitting.

8.

Using the original fittings, install the air supply line into the 
remaining T-fitting port.

9.

Charge the system to cut-out pressure and use a soap solution 
to test the T-fitting for air leaks. The vehicle may then be 
returned to temporary service.

CAUTION

This is a temporary bypass of the air dryer, and full repair of 
the unit must be carried out at the earliest opportunity. Long 
term use of the vehicle with the air dryer bypassed could 
result in excessive moisture build up in the air system.

Drain Air Reservoirs Daily Until Repairs are 
Completed

CAUTION

Long term use of the vehicle with the air dryer bypassed could 
result in excessive moisture build up in the air system.

Once the air dryer is removed, contaminants will enter the air 
system. Therefore, you will need to manually drain the reservoirs 
daily until the repairs are completed.

1.

At end of each working day, park the vehicle and slowly drain 
pressure through the drain valves. Leave the valves open to the 
atmosphere for several hours if possible.

2.

When repairs are completed, be sure to check that all 
reservoirs (including the air dryer) are emptied of all 
contaminants.

Figure 8.1

400

9

783

a

T-FITTING

Summary of Contents for 1200E

Page 1: ...Maintenance Manual 34 System Saver Series Single Cartridge Air Dryers System Saver Series 1200E P U 1800E P U 1200 Plus MCP Revised 03 16...

Page 2: ...azards are associated with the processes procedures described These may cause death or injury in any form if the instructions in the operational or procedural task are not followed precisely Warnings...

Page 3: ...Air Pressure Checks Operational Test for System Saver Series Air Dryers Regeneration and Purge Style 32 Pressure Controlled Check Valve Test Regeneration Style Only 34 Section 4 Appendix I Glossary D...

Page 4: ...Notes...

Page 5: ...ver 1000 1200 and 1200E Series and System Saver TWIN Air Dryers and Modification Instructions for Units Equipped with Alcohol Evaporators provides installation instructions To order literature visit o...

Page 6: ...sture is retained by the desiccant Moisture that condenses out also collects in the base of the dryer When the compressor unloads the water is expelled and dried air flows back through the dryer dryin...

Page 7: ...dryer at the inlet port Moisture laden air and contaminants pass through the desiccant Moisture is retained by desiccant moisture also collects in the base of the dryer Contaminants are removed as ai...

Page 8: ...10 psi 69 kPa is taken from the supply and secondary tanks for the regeneration Back flow dries desiccant preparing it for the next cycle On 1200 P UP 1800 P and UP Dry air flows from the separate pur...

Page 9: ...ection 6 Figure 1 5 Figure 1 5 1002141c PURGE VALVE EXHAUST COMPRESSOR DISCHARGE LINE COMPRESSOR CONTROL PURGE PORT COMPRESSOR INTAKE LINE PRESSURE CONTROLLED CHECK VALVE SUPPLY TANK SYSTEM RESERVOIRS...

Page 10: ...03 16 Figure 1 6 Figure 1 6 4012522a COMPRESSOR DISCHARGE LINE PURGE VALVE EXHAUST COMPRESSOR CONTROL PURGE PORT DRYER INLET PORT COMPRESSOR INTAKE LINE SUPPLY TANK SYSTEM RESERVOIRS ONE WAY CHECK VAL...

Page 11: ...Plus Series air dryers with Multi Circuit Protection Refer to Section 2 for instructions for removal of old parts and installation of new parts Figure 1 7 Figure 1 7 1002146b SYSTEM SAVER 1200 OR 180...

Page 12: ...nual 34 Revised 03 16 Figure 1 8 Figure 1 8 4007692a PRESSURE RELIEF VALVE DESICCANT CARTRIDGE SYSTEM SAVER 1200 PLUS SERIES AIR DRYER OUTLET CHECK VALVE ASSEMBLY GOVERNOR O RING PURGE VALVE ASSEMBLY...

Page 13: ...Figure 1 9 Figure 1 9 4011774a PURGE VALVE ASSEMBLY HEATER ASSEMBLY GOVERNOR OUTLET CHECK VALVE ASSEMBLY O RING TURBO CUT OFF VALVE ASSEMBLY PRESSURE RELIEF VALVE DRAIN VALVE DESICCANT CARTRIDGE SYST...

Page 14: ...the filter elements and desiccant needed to filter and dry system air Spin on spin off design allows quick and easy maintenance The System Saver 1800 Series cartridge is 3 2 inches 81 mm taller than...

Page 15: ...out the purge valve during a compressor unload cycle Figure 1 14 Figure 1 14 Pressure Controlled Check Valve PCCV Used with System Saver Series regeneration style air dryers The PCCV is usually mounte...

Page 16: ...type compressors Figure 1 19 Figure 1 19 ECON Valve This valve must be installed if System Saver 1200 Series air dryers NOT DESIGNATED E are used with Holset E type compressors This valve is not requ...

Page 17: ...dryer purge Figure 1 24 Figure 1 24 Pressure Protection Elements Ports that are located directly on the air dryer The eight ports are directly connected to the primary secondary and any auxiliary air...

Page 18: ...necessary Check the entire air system for leaks and repair as necessary When draining air tanks before servicing the air dryer check for water and or oil that may have accumulated in the tanks Water a...

Page 19: ...e cycle and flow is noticeably stronger at high engine RPM especially under load Turbo cut off valve leaking No pressure build up in system high compressor discharge line pressure Valve stuck in close...

Page 20: ...snap ring washer spring valve body and O ring 3 Clean and inspect the valve bore If the bore is damaged so that a tight seal cannot be maintained replace the air dryer 4 Install the new O ring on the...

Page 21: ...ems Parts To obtain this publication refer to the Service Notes page on the front inside cover of this manual NOTE Use the grease included with the replacement kit to lubricate O rings and seals Syste...

Page 22: ...ut out pressure of the compressor through signal lines from the system reservoir as well as the compressor head controlling onload and offload Use only the Meritor WABCO governor specified for use wit...

Page 23: ...e you have all of the parts required to replace the purge valve Use the grease included with the replacement kit to lubricate O rings and seals Do not grease the rubber seat If shims are included in t...

Page 24: ...bly Figure 2 16 Figure 2 16 10 Install spring in valve head fit valve head assembly into bore NOTE If shims are included in the replacement kit they must be installed above and below the spring If the...

Page 25: ...e all of the parts required to replace the bypass valve Use the grease included with the replacement kit to lubricate O rings and seals Figure 2 19 2 Remove the snap ring cover spring and valve body 3...

Page 26: ...e relief valve in the UP position or within 30 of vertical Figure 2 22 If not installed in the correct position serious personal injury and damage can result NOTE The threads on the replacement pressu...

Page 27: ...lug from the heater receptacle 3 Remove the three mounting bolts Remove the air dryer from its mounting location Figure 2 24 and Figure 2 25 Figure 2 24 Figure 2 25 4 Attach the new unit to the frame...

Page 28: ...by jacks Jacks can slip and fall over Serious personal injury and damage to components can result NOTE The pressure protection elements are not serviceable on the System Saver 1200 Plus with MCP The e...

Page 29: ...the compressor discharge line is long enough to keep inlet air below 175 F 80 C Figure 3 1 Refer to Section 5 Figure 3 1 Extreme Cold Make sure the air dryer heater is in good working order by runnin...

Page 30: ...replace if necessary Make sure governor to dryer port 4 line is free of water oil Remove and inspect purge valve and clean water oil from top of piston Debris under purge valve seat such as particles...

Page 31: ...rflow from purge valve after initial purge blast dryer decompression Air dryer not connected to supply tank or connections reversed at dryer Yes No Verify proper dryer installation per system diagram...

Page 32: ...s Yes Inspect compressor Repair replace per manufacturer s instructions Air flows out of purge valve entire time compressor is unloaded NOTE With U Series air dryers the compressor unloads through the...

Page 33: ...Yes Yes Inspect valve bore for wear If a new turbo cut off valve does not seal in a clean lubricated bore replace the air dryer Piston is broken Yes Yes Replace the turbo cut off valve Air dryer froze...

Page 34: ...Water in tanks often following aftermarket installation or when dryer is a replacement for a competitive brand Pressure controlled check valve not installed in correct tank or not installed at all Yes...

Page 35: ...st of air followed by a mild flow which will last 10 45 seconds 5 Shut off the engine 6 Apply a soap solution to each connection that contains pressurized air Check the connections to see if soap solu...

Page 36: ...ther air system problems or the pressure controlled check valve is not operating correctly Identify and repair all air leaks and air system problems Clean the Regeneration and Outlet Check valves Disc...

Page 37: ...valve located between the air dryer and the secondary air tank usually at the supply tank Secondary air gauge not plumbed to the secondary air system Use a calibrated air gauge in the secondary tank...

Page 38: ...re level in the air system supply tank which triggers the compressor unload cycle Dedicated Purge Tank A separate air tank used exclusively for holding air used in an air drying cycle This tank elimin...

Page 39: ...here are no valves or other devices in the dryer to supply tank line to prohibit or restrict the flow of air back from the supply tank to the air dryer Feed purge valve by a direct line from the air g...

Page 40: ...mal running Two minutes maximum Occasional three times per day maximum Seven minutes Compressor unloaded time Minimum for purge cycle 20 seconds Maximum duty cycle Compressor on time total running tim...

Page 41: ...valve eliminates the need for the external Econ valve Figure 6 2 Figure 6 1 PURGE VALVE EXHAUST COMPRESSOR DISCHARGE LINE COMPRESSOR COMPRESSOR INTAKE LINE PRESSURE CONTROLLED CHECK VALVE SUPPLY TANK...

Page 42: ...s manual for installation instructions To replace an ECON valve that is mounted directly to the air dryer follow these instructions 1 Unscrew and remove all of the lines from the Econ valve at the ai...

Page 43: ...place the Econ valve assembly on Meritor WABCO System Saver 1200E air dryers follow these instructions 1 Remove the Econ valve assembly A Using a flare wrench loosen the compression nuts on each end o...

Page 44: ...ications following the torque instructions in the kit Alcohol Evaporator Check the vehicle s air system for an alcohol evaporator NOTE Typically an alcohol evaporator will be installed in the line bet...

Page 45: ...E COMPRESSOR COMPRESSOR INTAKE LINE PRESSURE CONTROLLED CHECK VALVE SUPPLY TANK WET SYSTEM RESERVOIR INTERNAL CHECK VALVE DRYER INLET PORT UNLOADER LINE RESERVOIR TO GOVERNOR LINE 1800 1200 SYSTEM RES...

Page 46: ...GE LINE COMPRESSOR COMPRESSOR INTAKE LINE PRESSURE CONTROLLED CHECK VALVE SUPPLY TANK WET SYSTEM RESERVOIR INTERNAL CHECK VALVE DRYER INLET PORT UNLOADER LINE 1800 1200 SYSTEM RESERVOIR SUPPLY LINE DR...

Page 47: ...em Saver Series Single Cartridge Air Dryer Component Replacement Guide Dedicated Purge Figure 6 9 Figure 6 9 O RING HEATER ASSEMBLY DESICCANT CARTRIDGE PRESSURE RELIEF VALVE PURGE VALVE ASSEMBLY OUTLE...

Page 48: ...ge Lube and install O ring Install replacement cartridge T PRESSURE RELIEF VALVE Unscrew and remove old valve Screw replacement valve into dryer or Street Tee fitting Do not exceed recommended torque...

Page 49: ...Revised 03 16 7 Appendix IV Exploded View of System Saver 1200 Plus Series Air Dryer Figure 7 1 Figure 7 1 4007692a PRESSURE RELIEF VALVE DESICCANT CARTRIDGE SYSTEM SAVER 1200 PLUS SERIES AIR DRYER O...

Page 50: ...to prevent the vehicle from moving 3 Drain the entire air system Open all of the drain valves on all of the reservoirs 4 Ensure that all residual pressure has been released and the air dryer has been...

Page 51: ...ndix VI Exploded View of System Saver 1200 Plus Series with Multi Circuit Protection Figure 9 1 Figure 9 1 4011774a PURGE VALVE ASSEMBLY HEATER ASSEMBLY GOVERNOR OUTLET CHECK VALVE ASSEMBLY O RING TUR...

Page 52: ...Meritor WABCO Vehicle Control Systems 2135 West Maple Road Printed in USA Troy MI 48084 7121 866 OnTrac1 668 7221 Copyright 2016 Revised 03 16 meritorwabco com Meritor Inc Maintenance Manual 34 16579...

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