Piper Aircraft Corporation Malibu Mirage PA-46-350P, Airplane Maintenance Manual

Page: 334 / 1956

PAGE 16
Feb 28/07
2E8
21-50-00
PIPER AIRCRAFT, INC.
PA-46-350P, MALIBU MIRAGE
MAINTENANCE MANUAL
(2) Evacuating the System
If the system has been operated in a discharged condition or anytime the system has been
open to atmospheric pressure, the receiver-dehydrator must be replaced and the system
evacuated to remove any trapped air and moisture which has entered it. A vacuum pump
capable of pulling 29 inches of mercury or better should be used. As the pressure in the air
conditioning system is lowered, the boiling temperature of the water (moisture) that may be
present is also lowered. This then forces any moisture, in the form of water vapor, out of the
system. Chart 4 demonstrates the effectiveness of moisture removal under a given vacuum.
(a) Using a Kent Moore J23500 or similar charging stand: (See Figure 4.)
Turn aircraft power OFF before beginning.
1 Remove the access panel at the rear of the cabin floor to gain access to the service
valves on the manifold assembly.
2 Remove the protective caps from the high and low side service ports on the manifold
assembly.
3 Close all valves on the charging stand.
4 Remove the protective cap from the vacuum pump outlet.
5 Connect the blue and red hoses to the service ports (see Figures 1 and 2).
6 Start the vacuum pump.
7 Open the valve on the vacuum pump. Open the low pressure control valve and the
vacuum control valve on the charging stand.
8 After five minutes of pump operation, the high pressure gauge should indicate
slightly below zero.
a If it doesn’t, stop the pump and eliminate the blockage in the system replacing
the faulty component, then repeat steps (1) - (8).
b If it does, open the high pressure control valve on the charging stand and
continue to evacuate the system.
9 Operate the vacuum pump for fifteen minutes, or until the compound gauge indicates
24 to 26 in. Hg. whichever occurs first.
COMPOUND GAUGE
READING IN INCHES
OF MERCURY VACUUM
System Vacuum
27.95
28.74
29.53
29.76
29.84
29.88
Boiling Point of Water (°F)
101
84
52
29
15
1
CHART 4
USING VACUUM TO EVACUATE MOISTURE
NOTE: Compound gauge reading will be approximately one inch lower, numerically, for
each 1000 feet elevation above sea level.