CAUTION: A small amount of refrigerant oil is
removed from the A/C system each time the refrig-
erant system is recovered and evacuated. Before
charging the A/C system, you MUST replenish any
oil lost during the recovery process. Refer the
equipment manufacturer instructions for more infor-
mation.
After the refrigerant system has been tested for
leaks an d evacu ated, a refriger ant charge can be
injected into the system . (Refer to 24 - HEATING &
AIR CONDITIONING/PLUMBING - SPECIFICA-
TIONS - CH ARGE CAPACITY)
A R-134a r efrigera nt recovery/recycling/charging
st ation that meets SAE St andard J 2210 must be
used t o charge the refrigera nt syst em with R-134a
refriger ant. Refer to the operat ing instr uction s sup-
plied by t he equ ipmen t manufact urer for proper car e
and use of this equipment .
PARTIAL CHARGE METHOD
The par tia l cha rge m ethod is used to add a par tial
charge to a refriger ant system that is low on refrig-
eran t. To perform t his procedur e the evaporator inlet
and outlet tu be tempera tur es are mea su red. Th e
temper ature difference is mea su red with a tempera -
ture m eter with on e or t wo clamp-on th ermocou ple
pr obes. Th e differ ence between th e eva por ator inlet
and outlet tube tem perat ures will determine the
amount of refr iger ant needed.
Before adding a pa rtial refr igerant charge, check
for refriger ant system leaks. (Refer to 24 - HEATING
& AIR CONDITIONING/P LUMBING - DIAGNOSIS
AND TE STING - REFRIGERANT SYSTEM LEAKS)
If a l eak is found, make t he n ecessary repa irs before
attem pt ing a full or partial refr igeran t charge.
(1) Attach a manifold gau ge set to the refrigera nt
system service ports.
(2) Attach th e two clamp-on ther mocouple probes
to th e inlet and outlet tu bes of th e eva por ator coil.
• If a single th ermocou ple probe is used, att ach
the probe to th e evapor ator inlet tube just befor e the
colla r of the refr igeran t line connect or fitting. The
pr obe m ust ma ke conta ct wit h the bottom surface of
the evapor ator in let tu be.
• If dual t hermocouple probes are used, att ach
pr obe 1 t o the evaporator in let tube, an d probe 2 t o
the evapor ator out let tu be. Atta ch both probes to the
evapor ator tubes just before the collar of th e refrig-
eran t line connector fittings. The probes must m ake
contact wit h th e bottom surfa ces of the evaporator
inlet and outlet tubes.
(3) Open all of th e windows or doors of t he passen-
ger compartment.
(4) Set t he A/C button on t he A/C Heater con trols
to th e on position, t he tempera ture control knob in
the full cool posit ion, select Recirculation Mode, and
place the blower motor switch in t he highest speed
position .
(5) St art th e engine an d hold the engin e idle speed
at 1,000 rpm. Allow the engine to wa rm up t o normal
operat ing temper atur e.
(6) The compressor clut ch m ay cycle, depending
upon ambient tem perat ure, humidity, and t he refr ig-
eran t system cha rge level.
(7) Hold the engine idle speed at 1,000 rpm.
(8) Allow three to five minutes for the refriger ant
system to st abilize, th en record the tem perat ures of
the evapor ator in let an d ou tlet tubes.
• If a single probe is used, record the tempera ture
of the evapor ator in let tu be. Th en remove the probe
from th e inlet tu be and at tach it to the evapora tor
outlet tube just befor e the collar of the refr iger ant
lin e connector fit ting. The probe must make conta ct
with the bottom su rface of the evaporator outlet t ube.
Allow the ther mocouple a nd met er time to sta bilize,
then recor d the temperature of the evapora tor outlet
tube. Subt ract t he inlet tube temper ature rea ding
from the outlet tube tem per ature rea ding.
• If dual pr obes ar e used, recor d the tem per atures
of bot h t he evaporator inlet an d ou tlet t ubes. Then
su btra ct the in let tube temperature rea ding from the
outlet tube tem per atu re reading.
(9) If the measur ed tem perat ure differ ential is
higher th an 22° C t o 26° C (40° F to 47° F), add 0.4
kilogr ams (14 ounces) of refriger ant.
(10) Allow th ree to five m inu tes for the refr iger ant
system to stabilize, then take a second set of th ermo-
couple mea suremen ts. Record t he temperatur e differ-
ence t o determ ine if an addit ional cha rge is requir ed.
(11) Record th e compressor dischar ge pressu re. If
the reading is h igh er th an t he pr essu re shown in the
Compressor Discharge Pr essu re Ch art, th e syst em
could be overcharged. If the r eadin g is equ al to, or
lower, tha n the pressure shown in the char t, continue
with t his procedu re.
Compressor Discharge Pressure Chart
Ambient Tempera-
ture
16°C
(60°F)
21°C
(70°F)
27°C
(80°F)
32°C
(90°F)
38°C
(100°F)
43°C
(110°F)
Compressor Dis-
charge Pressure
1378 kPa
(200 psi)
1516 kPa
(220 psi)
1723 kPa
(250psi)
1930 kPa
(280 psi)
2206 kPa
(320 psi)
2413 kPa
(350 psi)
VA PLUMBING 24 - 65
To Next Page
Loading...
