Section 22: HEATING AND AIR CONDITIONING
PA1562
16
CAUTION
The filter dryer must be changed each time a
line in the system is opened.
Procedure
1. Energize passengers ‘section liquid solenoid
valve.
2. Run the system for 10 minutes, shut it OFF,
then close the receiver tank outlet valve by
turning it clockwise, backseat the suction
service valve on the compressor, install an
appropriate pressure gauge set, and turn
the valve forward ¼ turn to enable a visual
check of the suction pressure.
3. Disconnect the “Low Pressure Switch”
connector (mounted near the A/C
compressor, and install a jumper wire.
NOTE
This jumper wire will allow the clutch to remain
engaged after pressure drops below 15 psi
(103,5 kPa).
4. Start the engine, press the “Passenger
ON/OFF” switch then adjust (lower)
temperature control
to maximum
A/C.
5. Run the compressor until pressure reaches
1-2 psi (7-14 kPa).
NOTE
During this operation, care must be taken not
to fill the receiver tank over the upper sight
glass. If so, stop process immediately. Always
allow refrigerant piping and units to warm up
to the ambient air temperature before opening
system or sweating will take place inside the
lines.
6. Stop engine, and close compressor outlet
valve by turning it clockwise until valve is
properly seated.
7. Close compressor suction valve by turning it
clockwise until it is properly seated.
8. Wait until pressure gauge reaches 1 to 2 psi
(7 to 14 kPa). To accelerate procedure,
lightly open compressor suction valve until
pressure reaches this value.
6.4 ADDING REFRIGERANT (VAPOR
STATE)
Use the suction service valve on the compressor
to add a small quantity of refrigerant to the
system. Backseat the valve and connect a
charging line from the refrigerant cylinder to the
valve. Tighten connection at level of refrigerant
cylinder and open tank end slightly to purge air
from the charging line. Tighten the charging line
at the compressor. Screw in the stem of suction
valve approximately two turns. Start the engine
and run at fast idle. Add sufficient refrigerant to
bring the level in lower sight glass of receiver
tank to mid-point. Always charge the system
with the cylinder upright and the valve on top to
avoid drawing liquid out of the cylinder.
6.5 EVACUATING SYSTEM
1. Open both receiver valves by turning “out”
(normal position).
2. Remove the caps from the two 90° adapters
on the suction, discharge valves and
connect two hoses to the vacuum.
3. Place the two compressor valves, suction
and discharge, in neutral position by turning
each one 3 to 4 turns “in” from the “out”
position.
4. Open the solenoid valve by energizing or
manually bypass.
5. Start the vacuum pump. Open the large
(suction) shutoff valve and close the small
vacuum gauge valve.
6. The pressure will drop to approximately 29
inches vacuum (14.2 psi or 97,9 kPa) (the
dial gauge only gives a general idea of the
absolute system pressure.
7. Backseat the compressor valves by turning
“out” all the way.
8. Shut down the vacuum pump.
9. Remove the hoses.
10. Reinstall the caps at the suction valve take-
off points.
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