Service Valves; Test Gauge And Manifold Set; Checking The System For Leaks; Leak Check - Method 1 - Piper Navajo Chieftain PA-31-350 Service Manual

NAVAJO CHIEFTAIN SERVICE MANUAL
14-94. SERVICE VALVES. (Refer to Figure 14-32.) Discharge andsuction valves arethree-position valves
mounted on each side of the compressor cylinder head. The suction side of the compressor is identified by the
"S" or word "SUCTION" cast in the cylinder head. The discharge side is identified by the letter "D" or word
"DISCHARGE
The purpose of the three-position valves is. to facilitate servicing of the system. By closing the valves
(front seated) the compressor is isolated from the rest of the system and oil can be checked on the
compressor without discharging the system.
When the stem is turned in, the valve is "FRONT SEATED" (the gauge port is open and the system is
closed) when the stem is turned out, the valve is "BACK SEATED," (the system is open). When the stem is
turned to the halfway position commonly known as being "CRACKED" (the gauge port is open to the
system). The "BACK SEATED" position is the normal valve position when the air conditioning system is in
service.
There are Schrader valves in the discharge and suction lines located on the left forward side of the
right nacelle. These valves are placed in this position to allow the necessary checks and services to be safely
made with the engine operating.
14-95. TEST GAUGE AND MANIFOLD SET. The proper testing and diagnosis of the air conditioning
system require that a manifold gauge set be attached to the system. This set consists of two gauges mounted to a
manifold. One gauge is a high pressure gauge used in the discharge side of the system. The other is a low
pressure gauge used in the suction side of the system. The manifold is a device having fittings for both gauges
and connection hoses with provisions for controlling the flow of refrigerant through the manifold. (See
Figures 14-33. 14-34 and 14-35.)
The center port of the manifold set is used for charging or evacuation procedures, or any other service
that may be necessary.
Both the high and low side of the manifold have hand shutoff valves. When the hand valve is turned all
the way in. in a clockwise direction. the manifold is closed. The pressures on that side of the system will.
however, be recorded on the gauge above the hose.
Cracking the hand valve, in the counterclockwise direction, opens the system to the middle service port of
the manifold set. This is desirable only when it is necessary to let refrigerant out or into the system. (Refer to
Figures 14-33. 14-35. and 14-36.)
14-96. CHECKING THE SYSTEM FOR LEAKS. There are several methods of doing this operation.
depending on the type of equipment which is available. Two methods of performing this check will be covered
in the following paragraphs.
14-97. LEAK CHECK - METHOD 1.
a. Connect the manifold gauge, set into the system and determine if there is any refrigerant in the system.
A minimum of 50 psi refrigerant pressure in the system is needed for leak detection. (Refer to Figure 14-33.)
b.
Purge the hoses of air by allowing some refrigerant to escape from the connections at the service
valves. Then tighten connections at the service valve.
c. Close the low side manifold valve and open the high side manifold valve. (Refer to Figure 14-35.)
d.
Open the refrigerant container service valve and allow the pressure at the low side gauge to reach
50 psi. at which time close the high side manifold valve.
e.
Close the refrigerant container service valve and remove the hose if no leaks are evident.
f.
It is advisable to use an electronic leak detector to check this system instead of an open flame
leak detector due to the possible presence of gasoline fumes in the engine nacelle.
g.
If any leaks are found, purge the system of refrigerant, make the necessary repairs and check the
compressor oil.
Reissued: 9/23/80
ACCESSORIES AND UTILITIES
4 G21