MCi Crusader II 1989 Maintenance Manual page 480

Date
1-1-89
Page _
_.:.1.:::..6·....;.1..:...o _ _
MC-9 MAINTENANCE MANUAL
5. Close the discharge valve ~t the compressor.
6. Close the suction valve at the compressor.
CAUTION: During this operation care
must be taken not to flll the receiver tank
over the top sight glass. It may be neces-
sary to partially vent the tank. Always
allow refrigerant piping and system
components to warm up to the ambient
air temperature before opening system
or sweating will take place inside the
lines with resultant system contamina-
tion.
ADDING REFRIGERANT
Always charge the system with the Freon cylinder upright
and the valve on top to avoid drawing liquid out of the
cylinder. When charging an empty system. weigh the
amount of Freon put into the system. This
will
eliminate any
possibility of overfilling. A full charge is exactly 24 pounds
(10.8 kg).
To add Freon to the system:
1 . Backseat the suction service valve on the compressor
and loosely connect a charging line from the Freon cylinder
to the valve.
2. Tighten the connection
at
Freon cylinder and open the
tank end slightly to purge air from the charging line.
3. Tighten the charging line connection at the compres-
sor.
4. Screw the stem of the suction valve in approximately
two turns.
5. Start the engine (compressor} and run at fast idle. Add
sufficient Freon to bring the level in lower sight glass in
receiver tank to mid-point.
AIR IN SYSTEM
The presence of air in the air conditioning system may be
determined by the following test procedure. To check for
air, the system must be off and cooled to ambient
temperature:
1. Connect test gauges to A/C compressor and record
suction pressure and discharge pressure (head pressure}.
2. Compare the readings. If the difference between the
two readings is greater than 5 psi (34.5 kPa}, air is present
and the system should be purged.
3. If the difference between suction and discharge pres-
sure is with in 5 psi, connect a gauge to the test fitting on the
main expansion valve and recorrl
thP.
pressure. Compare
this reading with the suction pre!
4. Check the pressure on the d s expansion valve in
the same manner. Compare the reading with the suction
pressure.
5. If there is more than a 5 psi (34.5 kPa) difference
between suction pressure and either expansion valve pres-
sure, air is present and the system should be evacuated.
EVACUATION OF AIR-CONDITIONING SYSTEM
1. Connect service gauges and backseat both the suction
and discharge valves on the compressor.
2. Remove protective caps from the service gauge pres-
sure tap ports on the suction and discharge valves.
3. Connect the gauge hoses loosely to the compressor
suction and discharge valves.
4. Connect the line from the gauge manifold to the
vacuum pump. Connection should be tight.
5.
Midseat the valves at the high and low sides of the
service gauge manifold.
6. Open the suction and discharge service valves slightly
to allow any Freon that might be remaining in the system to
escape to the atmosphere.
7. When you can no longer detect Freon gas escaping,
tighten the service hose connections.
8. Midseat the suction and discharge service valves.
9. Start vacuum pump and run until pressure in the sys-
tem is from 29.5 to 29.7 In-Hg, then run 4 to 5 minutes
longer.
To check the system, proceed as follows:
10. Close valve between manifold and pump.
11. Shut off pump and
wait
15 minutes. If the pressure
rises no more than 2 psi during that time period. the system
is dry and free of leaks. If the pressure rises more than 2 psi
and stops, it indicates there is moisture remaining in the
system and further evacuation is required. (Repeat steps
9-11.} If the pressure rises more than 2 psi and continues to
rise, it indicates a leak in the system.
12. If there are no leaks or moisture in the system, close
the suction and discharge service valves on the compressor.
To remove gauges, proceed as follows:
13. Start engine and compressor.
14. Backseat compressor discharge service valve.
15. Backseat both high and low side hand valves of gauge
manifold with discharge service valve backseated.
16. Backseat compressor suction valve.
17. Shut engine off. ·
18. ·Remove the hoses from the compressor.
NOTE: If hoses are attached to dummy
fittings on back of manifold, there will be
enough refrigerant left in the lines to give
a slight positive reading to prevent dirt
and moisture from entering the gauges.
CHARGING THE SYSTEM
When a system has been opened or if there is any ques-
tion about the air or moisture in the system, evacuate the
system. Charging of an evacuated system may be accomp-
lished by forcing liquid Freon 12 directly into the receiver
tank.
This may be accomplished by placing the refrigerant tank
upside down on a scale (bathroom type) with valving at the
bottom and liquid charging. This ensures that only liquid
enters the reservoir.
1. Backseat the
two
compressor shut-off valves (out}.
2. Install the test gauges at the shut-off valves noting that
the 400 psi (2.758 kPa) gauge is connected to the discharge.
3. Turn in the two shut-off valves 3 to 4 turns.
4. Open the lower receiver valve by turning all the way
out.
5. Backseat the upper receiver valve by turning all the
way out.
6. Remove the cover cap from the service fitting in the top
receiver valve.