Subaru XT 1988 Service Manual page 1039

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AIR CONDITIONING SYSTEM 4-7
Fig. 20
CHECKING FOR LEAKS
1 Oil separator
2 Double union
3 Flexible hose [1.5 m (4.9 ft)]
Connector pipe
L4497
Conduct a leak test whenever leakage of refrigerant is sus-
pected and when conducting service operations which are
accompanied by disassembly or loosening of connection
fittings.
Refrigerant is a colorless, odorless gas and leakage from
system is difficult to detect. Accordingly, the use of a leak
detector facilitates check for leaks. Two methods of checking
are available; one employs a halide leak detector which burns
propane gas or butane gas and the other is an electric type leak
detector.
Halide leak detector
Since the propane leak detector and butane leak detector are
the same in respect to their operation. this section describes
the operation of the propane leak detector.
The copper screen is heated by the burning of propane.
Refrigerant gas decomposes to color the flame when it con-
tacts the heated screen. The gas to be checked is drawn into
the sampling tube and sent out to the burner. A refrigerant
leak can clearly be detected by variations in the color of the
flame.
1 Copper reaction plate
2 Flame adjusting lines
3 Burner
4 Sampling tube
5 Strainer
6 Gas bomb
5
7
Flame adjuster
@
A26-Q41
Fig.
21
17
Propane type
Butane type
NO LEAK
Greenish blue Pale blue
SMALL LEAK
Yellow Bright blue
LARGE LEAK
Purple Vivid green
1) Discharge refrigerant in one or two seconds to ascertain
that system has sufficient pressure needed for leak detection.
Charge with 0.4 kg (0.9 Ib) of refrigerant, if necessary.
2) Light leak detector. Adjust the height of the flame be-
tween flame adjusting lines at the top and bottom of com-
bustion tube. A reaction plate will immediately become red
hot.
3) Place the end of sampling tube near the point of the sus-
pected leak in system.
a. Since refrigerant gas is heavier than air, small leaks can be
easily detected by placing sampling
tube
directly below the
check point.
b. Suitable ventilation is required. If refrigerant gas is mixed
with the surrounding air, leak detector will always indicate a
response and detection of the actual leak will be difficult
c. Never hold leak detector at an angle.
CAUTION:
a. Never inhale the fumes produced by combustion of refriger-
ant gas since they are toxic.
b. Never use halide torch in a place where combustible or ex·
plosive gas is present.
4) The flame will be almost colorless when there is no re-
frigerant gas being burned. When there is a small refrigerant gas
leak. the flame will be green or yellowgreen. When refrigerant
gas leakage is large, the flame will be brilliant blue or purple.
Since the color of the flame will be yellow when dust is
being burned or there is aging scale on copper reaction plate,
always keep the strainer of sampling tube and reaction plate
clean.
5) Major check points
(1) Compressor
• Compressor shaft seal (rotate the compressor by
hand)
• Oil filler plug
• Flexible hose connections
• Rear cover and side cover gaskets
• Service valve
(2) Condenser
• Condenser pipe fitting
• Condenser inlet and outlet pipe connections
(3) Piping
• O-ring section of high pressure and low pressure
flexible hose.