Section 3
Installing Replacement Parts
MM-34
Page 24
Revised 11-02
Testing the Meritor WABCO
System Saver Series Air Dryer
1.
Turn off the engine after the air system
reaches cut-out pressure (approximately
120 psi) and the air compressor has unloaded.
2.
Drain the primary air tank(s) down to 80 psi
or lower.
3.
Check the secondary tank air gauge. It should
read 95 ± 5 psi. This drop from cut-out
pressure to 95 ± 5 psi for this particular test is
normal for vehicles equipped with any Meritor
WABCO single cartridge air dryer and the
pressure-controlled check valve.
4.
If the secondary tank air gauge reading is
less than 90 psi, check to see if the
pressure-controlled check valve is installed
backwards. If so, install correctly and re-test.
If not, check for air leaks in the secondary air
system. If no significant air leaks are found,
then replace the valve and re-test.
5.
If the secondary tank air gauge reading
does not change, or the reading does not fall
below 100 psi, then check for one of the
possibilities listed above in Step 4. If none
of those possibilities is found, then the
pressure-controlled check valve may be
shutting off at 100 psi or higher. Replace the
valve and retest.
NOTE:
When checking air pressures during
these procedures, do not rely on cab air
gauges for accurate readings. Install a
calibrated air gauge (accurate to within 1 psi)
in the secondary air tank for making
determinations about the continued use or
replacement of any equipment.
