Chevrolet 10 1971 Series Chassis Service Manual Download Page 33

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HEATER AND AIR CONDITIONING 1A-15

• A five ampere time delay cartridge fuse has been

installed in the common line to protect the windings

of the compressor.

The fuse will blow if an ex

cessive load is placed on the pump. In the event the

fuse  is  blown,  replace  with a five  ampere time delay
fuse  -  do not use  a substitute fuse  as it will  result in
damage to the  starting windings.

• If the pump is being utilized to evacuate a burnt-out

system, a filter must be connected to the intake

fitting to prevent any sludge from contaminating the

working parts, which will result in malfunction of the

pump.

• Do not use the vacuum pump as an air compressor.

LEAK TESTING THE SYSTEM

Whenever a refrigerant leak is suspected in the system

or  a  service  operation  performed  which  results  in  dis
turbing  lines  or  connections,  it  is  advisable  to  test for
leaks.  Common  sense  should  be  the governing factor in
performing  any  leak  test,  since  the  necessity and extent

of any such test will, in general, depend upon the nature
of the complaint and the type of service performed on the
system.

NOTE:

The use of a leak detecting dye within

the system is not recommended because of the
following reasons:

1. Refrigerant leakage can exist without any oil leakage.

In this case the dye will not indicate the leak, how

ever, a torch detector will.

2. The addition of additives, other than inhibitors, may

alter the stability of the refrigeration system and
cause malfunctions.

3. Dye type leak detectors, which are insoluble, form a

curdle which can block the inlet screen of the ex

pansion valve.

Leak Detector

Tool J-6084 (fig. 24) is a propane gas-burning torch

which  is  used  to  locate  a  leak in any part of the  system.
Refrigerant  gas  drawn  into  the  sampling tube attached to
the  torch  will  cause  the  torch  flame  to  change  color in

proportion to the size of the leak.

Propane gas fuel

cylinders used with the torch are readily available com
mercially throughout the country.

CAUTION:

Do not use lighted detector in any

place where combustible or explosive gases,

dusts or vapors may be present.

Operating Detector

1. Determine if there is sufficient refrigerant in the

system for leak testing.

2. Open control valve only until a low hiss of gas is

heard, then light gas at opening in chimney.

3. Adjust flame until desired volume is obtained. This

is most satisfactory when blue flame is approxi

mately 3/8” above reactor plate. The reactor plate

will quickly heat to a cherry red.

4. Explore for leaks by moving the end of the sampling

hose around possible leak points in the system. Do

not pinch or kink hose.

NOTE:

Since R-12 is heavier than air, it is

good practice to place open end of sampling tube

Fig. 24—-Leak Detector

immediately below point being tested, particu
larly in cases of small leaks.

CAUTION:

Do_ not breathe the fumes that are

produced  by  the  burning  R-12  gas  in  the  de
tector  flame,  since  such  fumes  can  be  toxic  in
large  concentrations of R-12.

5. Watch for color changes.

The color of the flame

which passes through the reaction plate will change

to  green  or  yellow-green  when sampling hose draws
in  very  small  leaks  of  R-12.  Large  leaks  will be
indicated  by  a  change  in  color  to  a brilliant blue or
purple.  When  the  sampling  hose  passes  the  leak,
the  flame  will  clear  to  an  almost  colorless  pale
blue  again.  Observations  are  best  made in a semi
darkened  area.  If  the  flame  remains  yellow  when
unit  is  removed  from  leak,  insufficient  air  is being
drawn in or the  reactor plate is dirty.

NOTE:

A refrigerant leak in the high pressure

side  of  the  system  may be  more  easily detected
if  the  system  is  operated  for  a  few  minutes,
then  shut  off  and  checked  immediately  (before
system  pressures  equalize).  A  leak  on the low

pressure side may be more easily detected after
the engine has been shut off for several minutes

(system pressures equalized); this applies par

ticularly to the front seal.

AVAILABILITY OF REFRIGERANT-12

Refrigerant 12 is available in 30 lb. and in 15 oz. dis

posable containers.

Normally, air conditioning systems are charged making

use of the J-8393 Charging Station which uses the 30 lb-

container.

Evacuating and Charging Procedures are

noted later in this section.

The 15 oz. disposable cans are generally used for