MCi Crusader II 1989 Maintenance Manual page 150

Date
1-1-89
Page
4-20
MC-9 MAINTENANCE MANUAL
ADJUSTMENT
The pressure setting of the safety valve is stamped on the
cover wrench flat (closest to the pipe thread). The correct pres-
sure setting is 150 psi (1,035 kPa).
To adjust, the safety valve must be connected to an air
system with air pressure in excess of desired setting. It is impor-
tant that an accurate gauge be used to check pressure settings
while making adjustments.
,To raise pressure setting, loosen lock nut, turn adjusting nut
clockwise to obtain correct pressure setting and tighten lock
nut
To lower pressure setting, loosen lock nut, turn adjusting nut
counterclockwise to obtain correct pressure setting and tighten
lock nut
LOW AIR PRESSURE SWITCH AND
ALTERNATOR CONTROL
The low pressure switch and alternator control gives an
automatic warning to the driver when air pressure is below the
minimum for safe vehicle operation. It operates an electric
buzzer and warning lights.
When reservoir air pressure under the diaphragm is above
70-75 psi (483-517 kPa), the electrical contacts remain open
because the force exerted by the air pressure overcomes the
force exerted by the spring above the diaphragm. When the
reservoir air pressure drops below 70-75 psi (483-517 kPa). the
diaphragm spring exerts a force greater than the force exerted
by the air pressure below the diaphragm. This causes the
diaphragm to move down and close the electrical contact This
completes the electrical circuit to the buzzer and warning light
informing the driver of the impending loss of air pressure. It also
opens the alternator charging circuit.
OPERATION
Operation of the low a1 r pressure switch and alternator con-
trol may be checked by reducing the reservoir pressure
through application and release of the service brakes numer-
ous times. Observe the air pressure gauge and when the air
pressure drops below 70- 75 psi (483-517 kPa); the tell-tale
warning light and buzzer should come on.
The air gauge in the instrument panel reads dry tank pres-
sure. In order to ascertain it there is a sufficient supply of air
pressure to all accessories prior to driving the vehicle. the
buzzer will sound and the tell-tale warning light will flash until
100 psi (690 kPa) air pressure is reached in the dry air system.
AIR LINE CHECK VALVES
The in-line check valves are placed in an air line to allow air
flow in one direction and to prevent the flow of air in the oppo-
site direction. An arrow indicating the direction of airflow is cast
into the body of the valve.
Air !low in the normal direction moves the disc valve from its
seat and the flow is unobstructed. Flow in the reverse direction
is prevented by the seating of the disc valve. Refer to figures
4-21 and 4-22.
MAINTENANCE AND TESTING
Every six months. 1,800 operating hours or every 50.000
miles (80,000 km). disassemble. clean and inspect all parts.
Replace any parts showing signs of wear or deterioration.
Depending upon installation, it may be necessary to com-
pletely remove the check valve so that the following checks
may be made. With air pressure present at the outlet side of
check valve and the inlet side open, coat the open end of the
check valve with soap solution: a 1" bubble leakage is permit•
ted in not less than five seconds.
If the check valve leaks excessively, the valve should be
replaced with a new check valve or repaired.
REMOVAL AND DISASSEMBLY
1. Block the coach by means other than the brakes.
2. Apply parking brakes.
3. Vent all reservoirs.
4. Disconnect air lines and plug ends to prevent any foreign
particles from entering the system.
5. Check and. if necessary, clean or replace air tines to valve.
6. 'Unscrew cap nut from body and remove gasket.
7. Remove shims (if present). disc valve. valve seat (if pres-
ent) spring, and valve stop bushing (if present).
CLEANING AND INSPECTION
1. Wash all metal parts in cleaning solvent
2. Rubber parts should be wiped clean.
3. Inspect disc valve and seat for signs of wear or deteriora-
tion.
4. Check spring for cracks, corrosion or distortion.
5. Inspect body and cap nut for cracks or damage.
6. Replace all parts that are damaged or worn.
To reassemble. position parts in proper order in body, install
new grommet on cap nut screw cap nut into body and tighten
securely.
NOTE: Care should be taken that valve is
not lodged between capnut and body when
assembling.
1. Spring
3. Valve Stop Bushing
5. Discharge Valve
2. Body
4. 0-ring
6. Cop Nut
Figure 4-21. Main Air Supply Check Valve.