Subaru 1600 Service Manual page 565

HEATING, VENTILATING AND AIR-CONDITIONING SYSTEM
than a wen-trained serviceman should
not be allowed to handle the refrig-
erant.
6) Evacuating and Charging
System
During servicing, use caution to keep
air from getting into refrigerant.
When air enters the system, all refriger-
ant must be evacuated from system
prior to charging new refrigerant. Air
in refrigerant has the following delete-
rious effects:
1) Since the condensation tempera-
ture of the air is extremely low, the air
will not be condensed when refrigerant
gas is condensed in the condenser, and
the air will thus remain in gaseous
form. Consequently, the effective ther-
mal transmission area of condenser for
refrigerant gas will be reduced and
refrigerant gas to be condensed will be
reduced. The pressure rise will become
proportional to the volume of the air
in system.
Ila~k-sealed
(Full
C(1UIl,.r-
clockwise)
Low-pressure ~auge
(Compound pressure gauge)
2) When air and refrigerant are
mixed in system, a chemical reaction
will be produced and hydrochloric
acid which will adversely affect the
aluminum, copper, iron, and other
materials in system may be generated.
Handling manifold gauge
The pressure at the high- and low-sides
of system should be measured when
evacuating and charging refrigerant
and when diagnosing trouble in the
system. The manifold gauge is used for
these purposes. A manifold gauge has
two pressure gauges; a low pressure
gauge and a high pressure gauge. These
gauges are connected to the high-
and low-side service valves of system
through flexible charging hoses. The
construction of manifold gauge is
shown in Figure.
When valve stem is fully screwed, the
valve is front-seated and valve path and
the center path are blocked. When
valve stem is backed off, the paths are
opened.
High-pressure gJlIge
Fronl-S<!ated
(Full clockwise)
To low-side To vacuum pump or To high-side
service valve refrigerant can
~rvice
valve
Fig. 13-50
(Connection to service valve)
1) Fully close both valves of mani-
fold gauge. Connect high- and low-
pressure charging hoses to manifold
gauge.
A26-028
2) Remove caps from service valves.
Connect high- and low-pressure charg-
ing hoses to service valves in system.
The refrigerant gas will be discharged
since check valve is open when pres-
sing charging hose onto service valve.
13-20
3) Next, loosen the connection fit-
ting
of
charging hose at manifold
gauge side for 2 to 3 seconds to purge
any air inside charging hose by the
pressurized gas in system_
(Disconnection from service valve)
1) Fully close both valves of mani-
fold gauge.
2) Disconnect two charging hoses
from service valves. At this time, the
gas will be discharged until check valve
is closed. Therefore, disconnect hose
quickly.
CAUTION:
Work with fingers protected with cloth
against frostbite by refrigerant.
Handling service valve
An automatic check valve is built into
service valve. When this valve presses
against the connection fitting, that is,
when charging hose is connected to
service valve, the valve is open. When
charging hose is disconnected, the
valve is closed automatically. Always
observe the following usage precau-
tions:
1) Always install valve cap after
using service valve.
When high speed operation is per-
formed without valve cap, a negative
pressure will gradually build up at the
low pressure side of system and air
may be sucked in. In addition, dirt and
dust will easily enter the valve result-
ing in foreign matter entering the
system.
2) Check valve will be half opened
during connection and disconnection
of charging hoses and refrigerant will
be forcefully discharged. Therefore,
connect and disconnect charging hoses
quickly while pressing flare nut of
charging hose against service valve.
CAUTION:
Work with fingers protected with cloth
against frostbite
by
refrigerant.
3) Since close contact between the
thread of valve cap and the thread of
service valve will prevent gas leakage,
keep these sections clean and free of
scratches and damage.
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