Meritor Wabco air dryer troubleshooting

ConditionPossible CausesActions Required
System Saver Twin air dryer does not work correctly.System Saver Twin air dryer mounted too close to heat source, such as engine exhaust stack or muffler.Verify correct installation.
Air delivered to System Saver Twin air dryer exceeds 175°F (79°C).Extend length of compressor discharge line as required, or install cooling coil.
Lines blocked with dirt.Clear or replace lines.
Loose fittings.Tighten or seal fittings.
System Saver Twin air dryer not switching every 50 to 60 seconds during compressor loaded cycle.Verify that the solenoid valve is operating correctly. See System Test Section III.
Water in air system.Desiccant saturated.Check timer (solenoid) and make necessary repairs.
NOTE: If timer is working correctly but System Saver Twin air dryer does not switch, check for sludge on valves. Clean the System Saver Twin air dryer.
If condition is not corrected:
• Check pistons or diaphragm and make necessary repairs.
• Replace cartridge®.
System Saver Twin air dryer leaks heavily from purge valve every other 60-second timer cycle.Incorrect air pressure maintained at System Saver Twin air dryer; 35-75 psi (241 -517 kPa) allows partial switching but does not seal valves for a second cycle.Install back-pressure control valve in system between the outlet of System Saver Twin air dryer and source of air take-off.
System Saver Twin air dryer frozen (water in System Saver Twin air dryer is freezing).Problem with heater assembly.Replace heater assembly.
Power supply to heater interrupted or short-circuited.Repair or replace power supply circuit. Replace fuse if needed.
Low voltage to heater unit.Ensure voltage is at least 10.5 volts (12-volt system) or 20 volts (24-volt system).
Wrong voltage System Saver Twin air dryer used (e.g., 24-volt in 12-volt system).Replace with correct System Saver Twin air dryer.
Excessive amount of oil released from exhaust of System Saver Twin air dryer. OR Sludge build-up on System Saver Twin air dryer base.Problem with air compressor.Repair or replace compressor. Replace desiccant cartridge(s).
Worn turbocharger oil seals (turbocharged compressors only.)Repair or replace turbocharger.
System Saver Twin air dryer does not purge when compressor unloads.Wrong air line or no air line connected to System Saver Twin air dryer Port 4.Connect air lines correctly.
Control line from governor unloaded port to System Saver Twin air dryer leaking.Repair any leaks.
Purge valve stuck closed.Replace purge valve.
Problem with governor.Repair or replace governor.
Cutout pressure never reached by air compressor. Check air system for leaks.
If condition is not corrected: Check/repair compressor.
Air pressure does not build in brake system.Leak in air system.Tighten all air line connections, test system for leaks, make necessary repairs.
Problem with compressor.Repair or replace the compressor.
Repair or replace problem air system components.
System Saver Twin air dryer control port (Port 4) plumbed wrong.Verify correct installation.
Obstruction in air compressor discharge line or System Saver Twin air dryer outlet line. Outlet check valve or turbo cut-off valve stuck in closed position.Check lines for crimps or blockages.
Make necessary repairs.
Air compressor discharge line plumbed to System Saver Twin air dryer outlet port (Port 2).Verify correct installation.
Make necessary repairs.
CTI Applications: Back-pressure control valve installed incorrectly.Verify installation of back-pressure control valve.
Faulty compressor discharge hose.Check for pinhole leaks along length of compressor discharge line from compressor to System Saver Twin air dryer. If found, replace hose. Make sure replacement hose is capable of sustained high temperature use.
Air continues to flow from purge valve after air compressor unloads.Compressor intake is turbocharged and there is no turbo cut-off valve in system.Install a New Generation System Saver Twin turbo cut-off air dryer.
The turbo cut-off valve is not working.Install a turbo cut-off valve repair kit.
Outlet check valve leaking accompanied by loss of pressure in supply reservoir.Check outlet check valve. Repair or replace as needed.