3
Troubleshooting and Testing
30
Meritor WABCO
Maintenance Manual 34 (Revised 03-16)
No air pressure
build-up in system.
Air dryer not plumbed correctly
(connections reversed).
Yes
Yes
Ensure 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.
Yes
Yes
Ensure dryer port 4 line is connected to
the “UNL” port of the air governor.
Air governor not working
properly.
Yes
Yes
Inspect 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.
Yes
Yes
Locate leak(s) and repair.
Air dryer leaks from purge valve.
Yes
Yes
Refer to purge valve conditions listed in
this chart.
Pressure protection elements
will not open.
Yes
Yes
Replace 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 correct tank or
not installed at all.
Yes
No
Install pressure-controlled check valve
in secondary tank.
Pressure-controlled check valve
properly installed, but one-way
check valve not removed.
Yes
No
Remove 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.
Yes
Yes
Replace desiccant. Inspect compressor
per manufacturer’s instructions.
Water in system
tanks.
Dessicant saturated.
Maintenance interval not
followed.
Yes
Yes
Replace dessicant cartridge.
Water in system
tanks, everything
else checks out
okay.
Dryer not suitable for
application.
Yes
Yes
Review the application guidelines. Refer
to TP-9672. For assistance, call the
Meritor OnTrac™ Customer Call Center
at 866-OnTrac1 (668-7221).
Condition
Possible Cause
Conditions May Occur In:
Solution
Regeneration
Style Air
Dryers
Dedicated
Purge Tank
Air Dryers
Summary of Contents for 1200 Plus MCP
Page 4: ...Notes...