MCi Crusader II 1989 Maintenance Manual page 494

Date
1-1-89
Page __
16_-2_4 _ _
MC-9 MAINTENANCE MANUAL
4. Turn the adjusting nut until-the needle on the service
gauge "jumps" to 36 psi (248 kPa).
5. If the unloader loads above or below 36 psi (248 kPa),
adjust the differential screw until the desired setting is
reached.
6. Once the adjustments have been made, tighten the jam
nut against the adjusting nut, ensuring the adjusting nut
does not move. Replace the differential adjustment screw
cap.
The procedure for setting the curb side unloader is iden-
tical except for the following substitution for steps 3 and 4.
Partially frontseatthesuction servicevalve until the pres-
sure in the service gauge reads 24 psi (165.6 kPa). Turn in
the adjusting nut until the needle on the service gauge
"jumps" to 30 psi (207 kPa).
COMPRESSOR OIL LEVEL CH ECK- Perform this produre:
1. Operate coach engine at fast idle with A/C switch ON
for at least 20 minutes. Shut engine off.
2. Open rear and right side engine compartment doors.
Sight gauges are located on both sides of compressor
crankcase. Oil level is correct when engine side sight gauge
is full and curb side sight gauge is empty.
3. If below correct oil level, check freon level before
adding oil.
4. If adding oil is required, proceed with the following.
ADDING OIL:
1. Backseat suction service valve and install low pressure
service gauge hose into suction service valve fitting. Front-
seat both sides of service gauge. Attach hose to middle port
of service gauge manifold and completely submerge the
other end in oil supply.
2. Disconnect liquid line solenoid wire, stud 11 in A/C
junction box.
3. Connect jumper wire between horizontal studs 1 and 2
in remote control box.
NOTE: The preceding wiring changes will
allow the clutch to remain engaged after
pressure drops below 15 psi (103.5 kPa). It
is necessary for the compressor to pump
down Into a vacuum to add oil In this
manner.
4. Frontseat suction service valve and crack open the low
pressure service gauge to purge the oil supply line. After
purging line, frontseat service gauge.
5. Start engine and actuate air conditioning system.
6. When pressure in service gauge reads a vacuum, crack
open the service gauge to allow oil to be drawn into com-
pressor. When desired amount of oil is added, frontseat
gauge.
7. Completely backseat suction service valve, discon-
nect jumper in remote control box and connect liquid line
solenoid in A/C junction box.
8. Run A/C system ~5-20 minutes and check oil level.
9. It more oil is needed, repeat procedure.
A pressurized oil pump that overcomes compressor
pressure and forces oil into the crankcase may also be
used. For further details, consult service department.
HI & LO PRESSURE SWITCH TESTS AND
UNLOADER CHECK
HI PRESSURE SWITCH TEST:
1. Connect high pressure service gauge to discharge
service valve test fitting; open or cover the condenser door.
2. With engine operating at fast idle, high pressure switch
should open at 300 .t 10 psi (2,070 ± 69 kPa) and cause
compressor clutch to disengage.
NOTE: Observe front plate of clutch.
When clutch is engaged. pulley and
front plate rotate together. When clutch
is disengaged pulley will rotate, but front
plate will not.
3. Close, or uncover the condenser door. Observe pres-
sure gauge and front plate of clutch at 190 .t 10 psi (1,310 ±
69 kPa) pressure switch should close and clutch should
engage.
LO PRESSURE SWITCH TEST:
1. Connect low pressure service gauge to suction service
valve test fitting.
2. Partially frontseat service valve until suction pressure
reads5.t3 psi {34.5±20.7 kPa). Low pressure switch should
open, clutch should disengage.
3. Slowly backseat suction service valve. Observe service
gauge and front plate of clutch. When pressure reads 20 ±3
psi {137.9 ±20. 7 kPa) switch should close and clutch should
engage.
CMECK UNLOADER OPERATION:
1. Operate engine at fast idle with A/C system ON, con-
denser door closed, and service gauges installed in suction
and discharge service valves.
2. Partially frontseat suction service valve and observe
the service gauges to determine pressure at which unload-
ers operate.
The engine side bank should load at 36 psi {248 kPa) and
unload at 30 psi {207 kPa). The curb side bank should load
at 30 psi (207 kPa) and unload at 24 psi {165.6 kPa). Load
and unload pressures are adjusted at the cylinder_ head
control set point adjust nuts {figure 16-22).
COMPRESSOR REMOVAL
1. If the compressor is inoperative, frontseat the suction
and discharge service valves to trap the refrigerant in the
system. If the compressor will operate, pump down the air
conditioning system; then, frontseat the suction and dis-
charge service valves.
2. Slowly loosen plug in gauge connection on suction
and discharge service valves and bleed refrigerant pressure
to atmosphere.
3. Loosen the capscrews that mount the suction and dis-
charge service valves, and tap the valves with a hammer to
free them from the mounting flanges. Remove capscrews
and service valves, but do not remove hoses from valves.
4. Disconnect electrical leads to compressor.
5. To remove the compressor drive belts, exhaust the air
from the belt tensioning cylinder by opening the valve