Mooney M20TN, Service And Maintenance Manual

Page: 162 / 1169

MOONEY AVIATION COMPANY, INC.
M20TN SERVICE & MAINTENANCE MANUAL
Page
Date
10
2006
Rev Date
21--52--02 -- SYSTEM (R--134a) EVACUATION
PROCEDURE
Prior to charging the system with refrigerant, the sys-
tem must be evacuated for a minimum of 45 minutes to
remove air and moisture which can cause the system
to perform incorrectly if not completely removed from
system.
1. Verify power to system is OFF.
2. If required, perform leak check procedure de-
scribed in Section 21--51--02.
3. Connect charging manifold to service ports (ref.
Section 21--51--02, 4 through 6.
4. Connect manifold charging (YELLOW) hose to
vacuum pump and turn pump ON.
NOTE:
An adapter may be required to allow vacuum
pump hookup.
5. Open both valves on charging manifold and ob-
serve gauges.
NOTE:
Low pressure gauge ”BLUE”, will indicate vacu-
um on lower range of gauge.
6. Evacuate system for 30 full minutes. System vacu-
um should attain 25/27 in. hg. in 10 to 15 minutes.
7. Continue evacuating for an additional 15 minutes.
System should obtain 29--30 in. Hg. within that time
frame.
8. Close manifold valves and shut vacuum pump
OFF. Vacuum in system must not change within 5 min-
utes.
-- CAUTION --
Any change in vacuum pressure or failure to
achieve a minimum system pressure of 29 in. hg.
vacuum indicates the presence of a plumbing
leak. Repeat leak check procedure; locate and
repair all leaks.
9. Disconnect manifold YELLOW service hose. Sys-
tem is ready for refrigerant charging.
NOTE:
Excessive water and/or air in the system will
cause pressure to rise/expansion valve freeze--
up.
21--52--03 -- REFRIGERANT CHARGING PROCE-
DURE
Charging the system with refrigerant is required on a
new system installation or when ”topping off” an exist-
ing system. There are various methods of charging re-
frigerant into the air conditioning system. These in-
clude using refrigerant recovery/recycle units, using a
charging cylinder, and direct charging using a scale.
Refer to manufacturer’s instruction manual for recov-
ery unit handling and operation.
NOTE:
Two people are required for the following proce-
dure.
1. Verify that all electrical power to the system is OFF.
2. If required, repeat leak check and evacuation pro-
cedures.
-- CAUTION --
Eye and hand protection must be worn during
this procedure.
3. Connect manifold charging hose (YELLOW) to
R--134a cylinder shutoff valve and open valve.
4. Crack hose fitting at manifold to purge air from
hose until refrigerant is obviously venting. If system re-
frigerant charge is to be recorded, place refrigerant
container on a 0--50 lb. scale and record initial weight
(Full system charge is approximately 2.2 lbs. of
R--134a).
5. Open both gauge valves on charging manifold and
allow refrigerant gas to enter system. Continue adding
refrigerant until system internal pressure has stabi-
lized.
6. Close manifold valves and verify system internal
pressure is 50 PSIG or greater.
NOTE:
If internal pressure is not above 50 PSIG, the low
pressure cutout switch will not close. To assure
an internal pressure of 50 PSIG, the R--134a cyl-
inder must be heated to obtain a charge pressure
of 70 -- 80 PSIG.
-- CAUTION --
Do not heat R--134a container with open flame;
container damage may result and possible injury
to operator. Heat with warm water or room tem-
perature. Do not store or heat refrigerant contain-
er at temperatures above 125
o
F.
7. Move aircraft to run--up area.
8. Start aircraft engine. Select ”MAX” on air condi-
tioner switch. Idle aircraft engine at 1200--1800 RPM.
Verify Alternator is charging.
-- CAUTION --
Do not operate system with high pressure (RED)
valve open on the charging manifold gauge set.
9. With system operating, observe the system dis-
charge and suction pressure values and refrigerant
condition in the receiver--dryer sight glass.
NOTE:
A flashlight and inspection mirror are required to
observe sight glass during the system charging
procedure. Excessive bubbles in the sight glass
indicate a low refrigerant level.
10. With the R--134a cylinder connected to the
charging hose, charging container shutoff valve open
and hose purged, slowly open the suction manifold
21--51--02
AUGUST 2010