Chevrolet 10 Series 1970, Service Manual

Page: 47 / 671

HEATER AND AIR CONDITIONING 1A-17
• A fiv e am pere tim e delay ca rtrid ge fuse has been
in stalled in the common line to p rotect the windings
of the co m p ressor.
The fuse w ill blow if an ex­
c e s s iv e load is placed on the pump. In the event the
fuse is blown, rep lace with a fiv e am pere tim e delay
fuse - do not use a substitute fuse as it w ill resu lt in
damage to the starting windings.
• If the pump is being u tilized to evacuate a burnt-out
system , a filt e r must be connected to the intake
fittin g to p reven t any sludge fro m contaminating the
working parts, which w ill resu lt in malfunction of the
pump.
• Do not use the vacuum pump as an a ir com p ressor.
LEAK TESTING THE SYSTEM
W h en ever a re frig e ra n t leak is suspected in the system
o r a s e r v ic e operation p e rfo rm e d which resu lts in d is­
turbing lin es o r connections, it is advisable to test fo r
leak s.
Common sense should be the governing fa cto r in
p e rfo rm in g any leak test, since the n ecessity and extent
o f any such test w ill, in gen era l, depend upon the nature
of the com plaint and the type of s e r v ic e p erfo rm ed on the
system .
NOTE: The use of a leak detecting dye within
the system is not recom m ended because of the
follow in g reasons:
1. R e frig e ra n t leakage can exist without any o il leakage.
In this case the dye w ill not indicate the leak, how­
e v e r, a torch detector w ill.
2. The addition of additives, other than in h ibitors, may
a lte r the stability of the r e frig e ra tio n system and
cause malfunctions.
3. Dye type leak d etectors, which are insoluble, fo rm a
curdle which can block the inlet screen of the ex­
pansion valve.
Leak Detector
T o o l J-6084 (fig . 27) is a propane gas-burning torch
which is used to locate a leak in any part of the system .
R e frig e ra n t gas drawn into the sam pling tube attached to
the torch w ill cause the torch fla m e to change c o lo r in
p rop ortion to the s ize of the leak.
Propane gas fuel
c y lin d e rs used with the torch a re re a d ily available com ­
m e r c ia lly throughout the country.
C A U TIO N : Do not use lighted detector in any
place w here com bustible o r exp losive gases,
dusts o r vapors m ay be present.
O p eratin g Detector
1. D eterm ine i f there is su fficien t re frig e ra n t in the
system fo r leak testing.
2. Open control va lve only until a low hiss of gas is
heard, then light gas at opening in chimney.
3. Adjust fla m e until d e s ire d volum e is obtained. This
is m ost sa tisfa ctory when blue flam e is approxi­
m a tely 3/8" above re a c to r plate. The reaction plate
w ill quickly heat to a c h erry red.
4. E xp lore fo r leaks by m oving the end of the sam pling
hose around possible leak points in the system . Do
not pinch o r kink hose.
NOTE: Since R-12 is h ea vier than a ir, it is
good p ra ctice to p lace open end of sam pling tube
F ig . 2 7 — Leak D e te c to r
im m ed ia tely below point being tested, particu ­
la r ly in cases of sm a ll leaks.
CAUTIO N: Do not breathe the fumes that are
produced by the burning R-12 gas in the de­
te c to r fla m e, since such fum es can be toxic in
la rg e concentrations o f R-12.
5. Watch fo r co lo r changes. The c o lo r of the flam e
which passes through the reaction plate w ill change
to green o r y e llo w -g re e n when sam pling hose draws
in v e r y sm all leaks of R-12.
L a rg e leaks w ill be
indicated by a change in color to a b rillia n t blue o r
purple. When the sam pling hose passes the leak,
the flam e w ill c le a r to an alm ost c o lo rle s s pale
blue again.
O bservations are best made in a s e m i­
darkened area. If the flam e rem ains y e llo w when
unit is rem oved fro m leak, insufficient a ir is being
drawn in o r the reaction plate is dirty.
NOTE: A re frig e ra n t leak in the high p ressu re
side of the system m ay be m ore ea s ily detected
i f the system is operated fo r a few minutes,
then shut o ff and checked im m ed iately (b efore
system p ressu res equ alize). A leak on the low
p ressu re side m ay be m ore ea sily detected a fter
the engine has been shut o ff fo r s e v e ra l minutes
(system p ressu res equalized); this applies p a r­
tic u la rly to the fron t seal.
AVAILABILITY OF REFRIGERANT-12
R e frig e ra n t 12 is available in 12 lb. and in 15 oz. d is­
posable containers.
N o rm a lly , a ir conditioning system s a re charged making
use of the J-8393 Charging Station which uses the 12 lb-
container. Evacuating and Charging P ro ced u res are
noted la te r in this section.
The 15 oz. disposable cans are gen era lly used fo r
m iscellan eou s operations such as flushing.
CHIMNEY
REACTION PLATE
S AM PLIN G TUBE
PROPANE G AS
CYLINDER
BURNER HEAD
BURNER TUBE
CHEVROLET TRUCK SERVICE MANUAL