3
Troubleshooting and Testing
29
Meritor WABCO
Maintenance Manual 34 (Revised 03-16)
Air leak at turbo
cut-off valve vent.
Rubber seal
damaged or missing.
NOTE:
As of Nov.
2009, the turbo
cut-off valve will have
an O-ring instead of a
lip seal.
Temperature of air coming into
dryer is too high — not enough
cooling takes place before dryer
inlet.
Yes
Yes
Move dryer farther from compressor.
Add additional compressor discharge
line before air dryer. Add cooling coil or
heat exchanger before air dryer.
NOTE:
Inlet air temperature must not
exceed 175
°
F (80
°
C).
Lip seal installed upside-down
on piston. Lip must face UP
(towards dryer).
Yes
Yes
Install lip seal correctly.
Valve bore worn excessively.
Yes
Yes
Inspect valve bore for wear. If a new
turbo cut-off valve does not seal in a
clean, lubricated bore, replace the air
dryer.
Piston is broken.
Yes
Yes
Replace the turbo cut-off valve.
Air dryer frozen
(water collecting in
base of dryer is
freezing).
No electrical power to heater
connector.
Yes
Yes
Check for a blown fuse. Repair heater
circuit.
NOTE:
There must be power to the
heater connector the entire time the
vehicle’s ignition is
ON
.
Low voltage to heater connector.
Yes
Yes
Repair cause of low voltage, such as
poor electrical ground, bad connections,
corroded wire splices, etc.
Heater assembly not working.
Yes
Yes
Replace heater assembly.
Wrong voltage air dryer used;
i.e., 12-volt air dryer used in a
24-volt system.
Yes
Yes
Replace with correct voltage air dryer.
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...
