Chevrolet 70 Series 1970, Service Manual

Page: 155 / 841

CAB AND BODY MOUNTINGS 1-124
CAUTION: Under no circumstances
should alcohol be used in the system in an
attempt to remove moisture, regardless
of the successful use of alcohol in other
refrigeration systems.
PREPARATION FOR EVACUATING
COMPLETE SYSTEM
1. Check the low p r e ssu r e gauge for proper
calibration, with the gauge disconnected from the
refrig era tio n sy stem . B e su re that the p oin ter on
the gauge in d icates to the center of ”0 ." Tap the
gauge a few tim e s lihgtly to be su re pointer is not
stick in g. If n e c e ssa r y , calibrate a s follow s:
a. R em ove the cover from the gauge.
b. Holding gauge pointer adjusting sc r e w fir m ­
ly with one hand, carefu lly fo r c e pointer in the
proper direction in the proper amount to p osition
the pointer through the center of the "O" p osition.
Tap gauge a few tim e s to be su re pointer on gauge
is not sticking. R eplace gauge cover.
2. If gauge s e t is not already connected to
c o m p r e sso r fittin gs, connect a s follow s (refe r to
fig .
2 1
):
a. C lo se hand sh u t-off v a lv es on gauge se t by
turning clock w ise.
b. R em ove caps from gauge fittings at com ­
p r e s s o r .
NOTE: To shorten evacuating and charging
tim e , the valve co re in each co m p resso r gauge
fitting can be unseated using Tool (J-22132-01).
The gauge lin e s a re than connected to the tool fit­
tin g s. Turn tool knobs counterclockw ise to unseat
c o r e s .
c. Attach Schrader valve adapter (J-5420) to
end of hose from suction valve low p r e ssu r e gauge
and connect this adapter fitted hose to the com ­
p r e s s o r suction gauge fitting or to Tool (J -2 2 1 3 2 -
0 1
) (if used).
a. Attach Schrader v a lv e adapter (J-9459) to
end of hose from co m p r esso r gauge and connect
th is adapter fitted hose to the d ischarge gauge fit­
ting or Tool (J-22132-01) (if used).
3. Attach a flex ib le gauge h ose to the center
fitting of the gauge se t and attach the other end of
th is hose to the vacuum pump (J-5428-02) (fig. 22).
4. The sy ste m can now be evacuated.
EVACUATING COMPLETE SYSTEM
1. Turn hand sh u t-off valve on low p r e ssu r e
gauge of gauge s e t to the full clock w ise (closed)
position .
2. Slowly turn valve on high p r e ssu r e gauge
counterclockw ise from the fu ll clo ck w ise p osition ,
letting any p r e ssu r e build-up esca p e com pletely.
C lo se high p r e ssu r e valve.
3. Check o il le v e l in vacuum pump (J-5428-02)
and add F rig id a ire-1 5 0 v isc o sity o il or equivalent,
if n e c e ssa r y , to bring to proper le v e l. Make su re
dust cap on d isch arge sid e of vacuum pump has
been rem oved.
4. Start the vacuum pump and slow ly open the
low and high p r e s s u r e sid e s of the m anifold gauge
s e t to avoid forcin g o il out of the refrigeration
sy ste m and the pump. P r e s s u r e is now being r e ­
duced on both s id e s of the refrig era tio n sy ste m .
NOTE: If o il is blown from the vacuum pump,
it should be r e fille d to the proper le v e l with F rig ­
id a ir e -1 5 0 v isc o sity o il or equivalent.
5. O bserve low p r e s s u r e gauge and operate
vacuum pump until gauge show s 26-28" vacuum .
Continue to run pump for ten additional m inutes.
NOTE: In a ll evacuating p roced u res the s p e c i­
fication of 26-28 inches of vacuum is u sed . T his
evacuation can only be attained at or near se a
le v e l. F or each 1,000 feet above s e a le v e l w here
th is operation is being perform ed, the sp ecifica tio n
should be low ered by one inch of m ercury vacuum.
F o r Example: At 5,000 fe e t elevation only 21
to 23 inches of vacuum can norm ally be obtained.
If vacuum cannot be pulled to the m inim um
sp ecifica tio n for the resp e c tiv e altitude, it indi­
c a tes a leak in the sy ste m , gauge connections o r a
d efective vacuum pump. In th is c a s e , it w ill be
n e c e ssa r y to check fo r lea k s a s outlined la te r , after
a sm a ll amount of R e fr ig e r a n t-12 has been added
to the low sid e of the sy ste m .
a. Turn the hand sh u t-off v a lv es at the low
and high p r e ssu r e gauge of the gauge s e t to the
full clo ck w ise p osition with the vacuum pump o p er­
ating, then stop pump.
b. Connect flex ib le lin e from cen ter fitting of
the gauge se t to refrigeran t container (container
should be at room tem perature).
NOTE: It may be n e c e ssa r y to u se reducer
fitting (J-8695-18) if attaching fle x ib le h ose to
drum -type refrigeran t container.
c . Open sh u t-off valve on container an d loosen
fle x ib le lin e fitting at center fitting at gauge s e t so
that refrig era n t w ill purge a ll a ir from lin e . Tighten
flex ib le fitting when certain a ll air has been purged
from lin e.
d. Open suction v a lv e on gauge s e t . T h is w ill
allow refrigeran t to p a s s from the container into
the sy ste m . When p r e s s u r e stop s r isin g , c lo se
suction valve on gauge se t and valve at refrigeran t
container (as refrig era n t container i s at room
tem perature, only a s m a ll refrigeran t charge w ill
enter the sy ste m ).
e. U sing leak d etector (J-6084) (fig. 24), check
a ll fittin g s in the sy ste m , co m p r e sso r shaft se a l
and on the gauge se t for evidence of leak age. When
gen eral area of leak has been found with the te st
torch, a liquid leak detector m ay be helpful in lo ­
cating the exact point of leak age. A fter leak has
been c o rrecte d , evacuate the sy ste m again fo r 15
to
2 0
m inutes.
CHEVROLET SERIES 70-90 HEAVY DUTY TRUCKSHOP MANUAL