Service Valves - Piper Navajo PA-31 Service Manual

407A
GAUGE PORT (TYPICAL)
FRONT SEATED POSITION
BACK SEATED POSITION
SERVICE VALVE DETAILS
"CRACKED" POSITION
Figure 14-27. Service Valves
14-67. SERVICE VALVES. (Refer to Figure 14-27.) Discharge and suction valves are three-position
valves mounted on each side of the compressor cylinder head. The suction side of the compressor is
identified by the letter "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.
NOTE
Use only a 1/4 inch square drive socket wrench when opening or
closing service valves. Do not use open end wrenches. Seat valves
to 12 ft lbs of torque.
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. There valves are placed in this position to allow the necessary checks and services to be safely made
with the engine operating.
14-68. 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 14-28, 14-29 and 14-30.
Reissued: 10/12/79
ACCESSORIES AND UTILITIES
PIPER NAVAJO SERVICE MANUAL
5G9