3
Troubleshooting and Testing
32
Meritor WABCO
Maintenance Manual 34 (Revised 03-16)
NOTE:
On System Saver 1200 Plus MCP air dryers, the
primary and secondary tanks may fill independently due to
pressure protection elements.
NOTE:
A 10 psi (69 kPa) drop in pressure in the secondary air
system is normal for Meritor WABCO System Saver Series
regeneration style air dryers.
NOTE:
On purge-tank style and System Saver 1200 Plus air
dryers, the regeneration cycle time is dependant on the size of
the tank. There should be no visible pressure drop during
regeneration. If there is a visible pressure drop, perform a
check valve leak test on the system check valves.
3.
Step 3 applies to regeneration style air dryers only.
If there
is no drop in pressure, one of the following conditions may
apply:
앫
Pressure-controlled check valve not installed, or installed
on wrong air tank.
앫
Pressure-controlled check valve installed to a one-way
check valve, instead of
in place of
a one-way check valve.
앫
There is another check valve located between the air dryer
and the secondary air tank, usually at the supply tank.
앫
Secondary air gauge not plumbed to the secondary air
system. Use a calibrated air gauge in the secondary tank to
check air pressure.
— Make the necessary installation changes or repairs and
repeat the operational test.
— If the secondary pressure drops 25 psi (172 kPa) or
more during the regeneration cycle — and there are no
other air-operated components using air during this
cycle — there are air leaks or other air system
problems, or the pressure-controlled check valve is not
operating correctly.
— Identify and repair all air leaks and air system problems.
— Clean the Regeneration and Outlet Check valves.
— Disconnect the compressor line from the air dryer (Dryer
Port 4). Check the compressor and governor per the
manufacturer’s recommendation.
Pressure-Controlled Check Valve Test —
Regeneration Style Only
1.
Turn off the engine after the air system reaches cut-out
pressure, approximately 120 psi (827 kPa), and the air
compressor has unloaded.
2.
Drain the supply tank down to 80 psi (552 kPa) or lower.
NOTE:
A drop from 120 to 95
±
5 psi (827 to 655 kPa) during
this test is normal for vehicles equipped with the System Saver
Series air dryer and a pressure-controlled check valve.
3.
Check the secondary tank air gauge. It should read 95
±
5 psi
(655 kPa). Figure 3.3.
Figure 3.3
4.
If the secondary tank air gauge reading is less than 90 psi
(62 kPa):
앫
Pressure-controlled check valve may be installed
backwards (arrow on valve must point toward host
reservoir). Make necessary corrections and retest.
앫
Check for leaks in the secondary air system. Identify and
repair any leaks.
앫
Pressure-controlled check valve may not be set correctly or
is not operating correctly. Replace the valve.
5.
If the secondary tank air gauge reading does not change — or
the reading does not drop below 100 psi (689 kPa), one of the
following conditions may apply:
앫
Pressure-controlled check valve not installed, or installed
on wrong air tank.
앫
Pressure-controlled check valve installed
TO
a one-way
check valve, rather than
IN PLACE OF
a one-way check
valve.
Figure 3.3
PSI
20
40
60
80
95
110
120
1002162a
PRIMARY
AIR SUPPLY
(RED)
SECONDARY
AIR SUPPLY
(WHITE)
Summary of Contents for 1200 Plus MCP
Page 4: ...Notes...
