Connect the air lines to the dryer as tagged
The purge valve will be open when the
Test the air dryer as outlined under Preventive
governor cut-out pressure is reached.
Maintenance and Serviceability Checks.
Allow two minutes for the purge cycle
before testing the check valve.
Check for excessive leakage at the purge
valve by coating the exhaust with a soap solution
Check for moisture in the air system by
while the compressor is loaded (compressing air).
opening the reservoir's drain cock or automatic drain
valve. In areas where more than approximately a 30
Check the operation of the safety valve by
degree range of temperature is common, small
amounts of water can accumulate in the air system
loaded (compressing air). There must be an exhaust
The presence of small
of air while the stem is held and the valve should
reseat when the stem is released.
should not be considered as an indication that the
dryer is not performing properly.
Check all lines and fittings leading to and from
the air dryer for leakage and integrity.
The desiccant cartridge should be replaced or
rebuilt when the desiccant is contaminated and does
Check the operation of the heater and
not have adequate water absorption capacity.
thermostat during cold weather operation. This can
However, the following checks should be made
be done by allowing the end cover assembly to cool
before replacing the desiccant cartridge to ensure
below 50 degrees F (10 degrees C) and feeling the
the water accumulation is not related to the items
end cover. When the ignition is turned ON, the end
cover should be warm to the touch within a few
moments. Warming should cease at about 85
An outside air source has been used to
degrees F (294 degrees C).
charge the system. This air did not pass
through the drying bed.
Air usage is exceptionally high and not
normal for a highway vehicle. This may be
due to accessory air demands or some
For more detailed information refer to the
unusual air requirement that does not allow the
applicable SM package.
compressor to load and unload (compressing
and non-compressing cycle) in a normal
fashion. Check for high air system leakage.
Chock the wheels.
The air dryer has been installed in a
system that has been previously used without
Deplete all pressure in both air systems.
an air dryer. This type system will be saturated
with moisture and several weeks of operation
Disconnect and tag all air lines from the
may be required to dry it out.
reservoir to be removed.
Location of the air dryer is too close (less
attaching the reservoir bracket to supporting
Check the mounting bolts for tightness. Check
the electrical connection to the dryer.
Remove the reservoir with the brackets from
Check the operation of the integral single
check valve. Build air system pressure to governor
If a new reservoir is to be installed, remove the
cut-out and observe the test air gauge installed in the
brackets, fittings, and components from the
No. 1 reservoir. A rapid loss of pressure could
indicate a failed check valve. This can be confirmed
by checking at the purge valve exhaust.