Air Dryer Diagnostics
Possible Cause
Solution
Purge valve is frozen open due to cold temperatures.
Inspect the heater and repair or replace as needed. Make sure the governor to dryer
port 4 line is free of oil and water.
Debris, such as particles from the fitting or air inlet line, under the purge valve
seat.
Disassemble and clean the purge valve. Make sure the purge valve is free of water
and oil from the top of the piston.
Purge valve washer installed upside-down.
Remove cartridge and clean the dryer sump.
Wrong air line connected to dryer port 4 (unloader port).
Make sure the lip on the aluminum washer is facing down and away from the dryer.
Purge valve snap ring does not sit fully in the groove.
If necessary, correct the air line installation.
Ensure the snap ring is fully seated in the groove.
Possible Cause
Solution
Outlet check valve not seating or regeneration valve not shutting off regeneration
airflow.
Remove and inspect the outlet check valve and regeneration valve diaphragm. Clean if
necessary and replace if worn or damaged.
Possible Cause
Solution
Outlet check valve not seating.
Inspect and replace outlet check valve if necessary.
Regeneration valve not closing off regeneration air flow correctly.
Swap regeneration valve.
Possible Cause
Solution
During the compressor unloaded cycle, high air system demands.
Air system capacity could be increased or reduce air demands.
Pressure-controlled check valve not installed or not working properly.
Check or replace the pressure-controlled check valve, if necessary.
Wrong (One-way) check valve installed in system reservoir instead of, or with,
pressure-controlled check valve.
Remove the one-way check valve and ensure proper installation of pressure-controlled
check valve.
Faulty Regeneration valve.
Remove the regeneration valve. Ensure that the diaphragm is clean and free of oil
and other debris. If no impurities are present, replace regeneration valve assembly.
Faulty Air governor.
Inspect and repair or replace as needed, per manufacturer’s instructions.
Possible Cause
Solution
Air dryer is not connected to the supply tank or the connections were reversed.
Ensure that the dyer was installed correctly, per the system diagram.
Faulty regeneration valve.
Swap regeneration valve.
Incorrect (One-way) check valve installed in supply tank.
Take out the one-way check valve.
Alcohol evaporator installed between dryer and supply tank.
Install a bypass line around the evaporator or remove the evaporator from the
system.
Possible Cause
Solution
Leak in line between governor and dryer port 4.
Repair air line.
Leak in line between supply tank and governor.
Repair leaks.
Air system leaks excessively.
Increase air system capacity or decrease air demand.
Excessive air system demands.
Inspect and replace outlet check valve if necessary.
Outlet check valve not sealing.
Replace regeneration valve.
Regeneration valve not shutting of properly.
Replace air governor.
Less than a 16 psi range on air governor.
Inspect compressor. Repair or replace compressor if necessary and per manufacturer’s
instructions.
Air compressor unloader(s) leaking.
Possible Cause
Solution
There is a kink or plug in the air line between governor and air dryer port 4.
Repair air line.
Purge valve wedged closed.
Replace purge valve.
Air governor not working properly.
Inspect air governor and repair or replace per manufacturer’s instructions.
Cut-out pressure never reached by air compressor.
Check for air leaks and repair if necessary. If there are no leaks in the system,
check the compressor output and repair or replace per manufacturer’s instructions.
Possible Cause
Solution
Turbo cut-off valve not sealing.
Replace the turbo cut-off valve.
Possible Cause
Solution
Non-1200E dryer installed, but Holset E-Type compressor used.
Replace with a System Saver 1200E air dryer.
Compressor not unloading completely when cut-out pressure is reached.
Inspect compressor and repair/replace per manufacturer’s instructions.
Possible Cause
Solution
Temperature of air coming into the dryer is too high – not enough cooling occurs
before dryer inlet.
Move the dryer farther from the compressor. Add additional compressor discharge line
before air dryer. Add cooling or heat exchanger before air dryer. (Note: Inlet air
temperature must not exceed 175°F)
Possible Cause
Solution
Lip seal installed upside-down on piston (lip must face up towards dryer).
Install lip seal facing up towards dryer.
Inspect the valve bore for wear. If a new turbo cut-off valve does not seal in a
clean, lubricated bore, replace the air dryer.
Possible Cause
Solution
Low voltage or no electrical power to heater connector.
Check for a blown fuse and repair heater circuit if necessary.
Heater assembly now working.
Note: During the entire duration that the vehicle ignition is “on”, there must be
power to the heater connector.
Wrong voltage air dryer used (for example, 12-volt air dryer used in a 24-volt
system).
Look for signs of low voltage, such as poor electrical ground, bad connections
corroded wire splices, etc. and repair.
Replace heater assembly.
Replace with correct voltage air dryer.
Possible Cause
Solution
Air dryer not plumber correctly (connections reversed).
Make sure that air dryer port 1 is plumbed to compressor discharge line, and air
dryer port 21 is connected to vehicle s supply tank.
Dryer port 4 connected to wrong air line.
Make sure that dryer port 4 line is connected to the “UNL” port of the air governor.
Air governor not working correctly.
Inspect governor per manufacturer s instructions and repair or replace if necessary.
Air system leaks, such as compressor discharge line, air dryer, reservoirs, brake or
suspension valves, etc.
Find the leak(s) and repair.
Air dryer leaks from purge valve.
See purge valve conditions listed in this chart
Possible Cause
Solution
Pressure-controlled check valve not installed in correct tank or not installed at
all.
Install pressure-controlled check valve in secondary tank.
Pressure-controlled check valve installed correctly, but one-way check valve not
removed.
Remove one-way check valve so that only the pressure-controlled check valve is
installed between the secondary tank and supply tank.
Possible Cause
Solution
Desiccant contaminated with oil.
Replace desiccant. Inspect the compressor per manufacturers instructions.
Non-1200E dryer installed, but Holset E-type compressor used.
Replace air dryer with a System Saver 1200E air dryer.
Possible Cause
Solution
Dryer not suitable for application.
Review application guidelines.