BRAKES-AIR
TRUCK SERVICE MANUAL
ridge to ascertain that the water accumulation is not
stem is released.
related to the following listed items:
6. Check all lines and fittings leading to and from the air
a. An outside air source has been used to charge
dryer for leakage and integrity.
the system. This air did not pass through the
drying bed.
7. Check the operation of the heater and thermostat
during cold weather operation. This can be done by
b. Air usage exceptionally high and not normal for a
allowing the end cover assembly to cool below 100 C
highway vehicle. This may be due to accessory
(500 F) and feeling the end cover when the ignition is
air demands or some unusual air requirement
turned on. The end cover should be warm to the
that does not allow the compressor to load and
touch within a few moments. Warming should cease
unload (compressing and non-compressing
at about 300 C (850 F).
cycle) in a normal fashion. Check for high air
system leakage.
The desiccant change interval may vary;
however, it is generally recommended that the desiccant
c. The air dryer has been installed in a system that
be replaced every 12 months (yearly). If experience has
has been previously used without an air dryer.
shown that extended or shortened life has resulted for a
This type system will be saturated with moisture
particular installation, then the yearly interval can be
and several weeks of operation may be required
increased or reduced accordingly.
to dry it out.
REMOVAL OF DESICCANT CARTRIDGE AD-1 & AD-2
d. Location of the air dryer is too close to the air
compressor. Refer to "Installation" section.
1. Make certain the vehicle is safely parked. Block the
wheels if necessary.
2. Check mounting bolts for tightness.
Check all air
and electrical connections.
2. Drain the air system completely being sure that the
lines leading into and out of the air dryer are at
3. Check the operation of the integral single check
atmospheric pressure.
valve in the AD-2 or the "in-line" check valve used
with AD-1. Build the air system, to governor cutout
3. Disconnect the air line from the end cover and mark
and observe the test air gauge installed in the
location of this port on the dryer.
supply reservoir. A rapid loss of pressure could
indicate a failed check valve.
This can be
4. Disconnect the heater wire.
confirmed by checking at the purge valve exhaust.
5. Loosen the three capscrews on the end cover and
NOTE: Purge valve will be open when governor
turn the retaining clamps aside (capscrews may be
cut-out pressure is reached. Allow two minutes
left finger tight).
for purge cycle before testing the check valve.
6. Locate the notch in the dryer shell. While pushing
4. Check for excessive leakage at the purge valve by
the end cover up into the dryer, insert the blade of a
coating the exhaust with a soap solution while the
screwdriver in the notch and slowly pry out the
compressor is loaded (compressing air).
retainer ring. Remove the end cover assembly and
set it aside temporarily.
5. Check the operation of the safety valve by pulling the
exposed stem while the compressor is loaded
7. Using a 3/4" socket wrench, remove the cartridge
(compressing air). There must be an exhaust of air
and desiccant sealing plate assembly.
while the stem is held and the valve should reseat
when the
NOTE: Be certain the desiccant sealing
plate assembly comes out with the
cartridge.
177