Wabco air dryer troubleshooting

The brand Wabco is Belgian. Its history began in the 1869. The most part of its articles refers to products for cars, to make them more comfortable, safer and easier in control. Thus, the company produces air dryers. Some innovations in this field belong to the brand. Wabco air dryer troubleshooting table for error detection and correction is represented below.

ConditionPossible CauseRegeneration Style Air DryersDedicated Purge Tank Air DryersSolution
Dryer leaks from purge valve during compressor loaded cycle. The leak may cause excessive compressor cycling or prevent the system from building air pressure.Purge valve frozen open (cold weather operation).YesYesCheck heater. Repair/replace if necessary. Make sure governor to dryer port 4 line is free of water/oil. nRemove and inspect purge valve and clean water/oil from top of piston.
Debris under purge valve seat, such as particles from fittings or air inlet line.YesYesDisassemble and dean purge valve. Remove cartridge and clean dryer sump area.
Purge valve washer installed upside-down.YesYesEnsure lip on aluminum washer faces DOWN, away from dryer.
Wrong air line connected to dryer port 4 (unloader port).YesYesVerify coned air line installation and correct as needed.
Purge valve snap ring not fully seated in groove.YesYesSeat snap ring fully into groove.
Regeneration cycle too long (more than 30 seconds), accompanied by loss of pressure in the supply tank.Outlet check valve not seating.YesYesInspect and replace outlet check valve as needed.
Regeneration valve not shutting off regeneration airflow.YesNoReplace regeneration valve.
Regeneration cycle too short (less than 10 seconds).High air system demands during compressor unloaded cyde.YesYesIncrease air system capacity or reduce air demands.
Pressure-controlled check valve not installed in system or not working properly.YesYesCheck and replace pressure-controlled check valve as needed.
One-way check valve installed in system reservoir instead of, or with, pressure-controlled check valve.YesNoRemove one-way check valve. Make sure pressure-controlled check valve is installed correctly.
Regeneration valve not working.YesNoRemove regeneration valve and clean oil from diaphragm. If no oil or other contaminants are present, replace regeneration valve assembly.
Air governor not working properly.YesYesInspect air governor. Repair/replace per manufacturer’s instructions.
Water in purge tank.Block in purge tank line.N/AYesClear blockage. Replace desiccant cartridge.
No regeneration cycle. No airflow from purge valve after initial purge blast (dryer decompression).Air dryer not connected to supply tank or connections reversed at dryer.YesNoVerify proper dryer installation per system diagram.
Regeneration valve not working.YesNoReplace regeneration valve.
One-way check valve installed in supply tank.YesNoRemove one-way check valve.
Alcohol evaporator installed between dryer and supply tank.YesNoInstall bypass line around evaporator or remove evaporator from system.
Blocked line/pinched line from purge tank.NoYesClear/repair line.
Air dryer does not purge when compressor unloads (no blast of air from purge valve).Air line between governor and air dryer port 4 kinked or plugged.YesYesRepair air line.
Purge valve stuck closed.YesYesReplace purge valve.
Air governor not working properly.YesYesInspect air governor. Repair/replace per manufacturer’s instructions.
Cut-out pressure never achieved by air compressor.YesYesCheck for air leaks in system and repair as needed. If no leaks in system, check compressor output. Repair/replace per manufacturer’s instructions.
Air dryer purges too often, perhaps as frequently as every 15 seconds, accompanied by excessive cycling of the compressor.Leak in line between governor and dryer port 4.YesNoRepair air line.
Leak in line between supply tank and governor.YesYesRepair air line.
Leaks in the air system.YesYesRepair leaks.
Excessive air system demands.YesYesIncrease air system capacity or reduce air demand.
Outlet check valve not seating.YesYesInspect and replace outlet check valve as needed.
Regeneration valve not shutting off properly.YesNoReplace regeneration valve.
Air governor has less than 16 psi (110 kPa) range.YesYesReplace air governor.
Leaking air compressor unloader(s).YesYesInspect compressor. Repair/replace per manufacturer’s instructions.
Air flows out of purge valve entire time compressor is unloaded.Turbo cut-off valve not sealing. Outlet check valve not seating.YesYesReplace turbo cut-off valve. Replace outlet check valve.
Rapid “spitting” of air from purge valve in small amounts. Frequency varies with engine speed.Holset E-type compressor used, but no Econ valve installed.YesYesInstall Econ valve to provide make-up air to compressor.
Compressor not completely unloading when cut-out pressure is reached.YesYesInspect compressor. Repair/replace per manufacturer’s instructions.
Air leak at turbo cut-off valve vent Rubber seal damaged or missing.Temperature of air coming into dryer is too high — not enough cooling takes place before dryer inlet.YesYesMove dryer farther from compressor. Add additional compressor discharge line before air dryer. Add cooling coil or heat exchanger before air dryer.
Lip seal installed upside-down on piston. Lip must face UP (towards dryer).YesYesInstall lip seal correctly.
Valve bore worn excessively.YesYesInspect 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.YesYesReplace the turbo cut-off valve.
Air dryer frozen (water collecting in base of dryer is freezing).No electrical power to heater connector.YesYesCheck for a blown fuse. Repair heater circuit. NOTE: There must be power to the heater connector the entire time the vehicle's ignition is ON.
Low voltage to heater connector.YesYesRepair cause of low voltage, such as poor electrical ground, bad connections, corroded wire splices, etc.
Heater assembly not working.YesYesReplace heater assembly.
Wrong voltage air dryer used; i.e., 12-volt air dryer used in a 24-volt system.YesYesReplace with conect voltage air dryer.
No air pressure build-up in system.Air dryer not plumbed correctly (connections reversed).YesYesEnsure compressor discharge line is plumbed to air dryer port 1, and air dryer port 21 is connected to vehicle's supply tank.
Wrong air line connected to dryer port 4.YesYesEnsure dryer port 4 line is connected to the *UNL’ port of the air governor.
Air governor not working properly.YesYesInspect governor per manufacturer’s instructions. Repair or replace as needed.
Air system leaks, such as compressor discharge line, air dryer, reservoirs, brake or suspension valves, etc.YesYesLocate leak(s) and repair.
Air dryer leaks from purge valve.YesYes
Pressure protection elements will not open.YesYesReplace the air dryer. The pressure protection elements are non-serviceable.
Water in tanks; often following aftermarket installation or when dryer is a replacement for a competitive brand.Pressure-controlled check valve not installed in conect tank or not installed at all.YesNoInstall pressure-controlled check valve in secondary tank.
Pressure-controlled check valve properly installed, but one-way check valve not removed.YesNoRemove one-way check valve so that only the pressure-controlled check valve is installed between the secondary tank and supply tank.
Water, oil, or sludge in air system tanks.Desiccant contaminated with oil.YesYesReplace desiccant. Inspect compressor per manufacturer’s instructions.
Water in system tanks.Dessicant saturated. Maintenance interval not followed.YesYesReplace dessicant cartridge.
Water in system tanks, everything else checks out okay.Dryer not suitable for application.YesYesReview the application guidelines. For assistance, call the Meritor OnTrac™ Customer Call Center