GMC 4000 Series Service Manual page 97

Sec. 1
Page 90
AIR CONDITIONING
(hand tight), then open valve quickly, admitting
several short blasts.
5. To reassem ble: Unthread burner head, in­
sert orifice block into burner tube, and thread
burner head onto burner tube with a wrench to
form a gas-tight joint.
Replacement parts can be obtained from Kent -
Moore Corp., Detroit, Michigan.
CHECKING FOR REFRIGERANT LEAKS
After the leak detector flame is adjusted,
check for refrigerant leaks in an area having a
minimum amount of air flow in the following man­
ner (see fig. 13):
Explore for leaks by moving end of sampling
tube around all connections and points where a
leak may be. Check around bottom of connections,
since Refrigerant-12 is heavier than air and will,
therefore, be more apparent at bottom of fitting.
The color of the flame will turn to a yellow-
green when a small leak is detected. Large leaks
will be indicated by a change in color to brilliant
blue or purple. When the suction hose is moved
away from the leak the flame will clear to an al­
most colorless pale blue again.
CAUTION: Do not breathe the fumes
and black smoke that are produced if
the leak is a big one. They are poison­
ous! Any time an open flame is used
near a vehicle there is a certain amount
of danger. Although the torch flame is
small and well protected, it is recom ­
mended that fire extinguisher be close
at hand for any emergency that might
arise.
LIQUID-TYPE LEAK DETECTORS
There are a number of fittings and places
throughout the air conditioning unit where a liquid
leak detector solution may be used to pinpoint leaks.
By merely applying solution to the area with the
swab that is usually attached to the bottle cap, bub­
bles will form within seconds if there is a leak.
For confined areas, such as sections of the
evaporator and condenser, the torch-type detector
is the only practical kind which should be used for
determining leaks.
ELECTRONIC LEAK DETECTOR
An electronic leak detector for detecting re­
frigerant leaks is also available. Instructions for
operation of this type detector are supplied with the
unit.
REPLACING COMPRESSOR
The com pressor removed must be closed im ­
mediately. See lower View of figure 14 which shows
G M C S E R V I C E M A N U A L
a closure plate which can be improvised and in­
stalled as shown.
more than two minutes, circulation of oil from the
com pressor to other components of the system will
require adjustment of the oil charge in the new
com pressor as explained previously, under "Re­
placing Components Other Than Compressor."
crankcase, the amount that has migrated to other
parts of the system, can be determined by subtract­
ing the amount drained from the original oil charge
of 11 fluid ozs. The amount of oil equal to this loss
shall be drained from the new com pressor assem ­
bly before it is installed.
REPLACING AN OPERABLE COMPRESSOR
placed for 10 minutes at 1500-2000 engine rpm, at
maximum refrigeration and blower at high speed:
DO NOT add any more oil to the com pressor than
is necessary or maximum cooling will be reduced.
pressor assembly.
zontal position with drain plug downward, drain
com pressor, measure quantity of oil drained and
then discard it.
save it.
(overhauled) com pressor.
add one extra oz. of oil. (More oil is retained in a
drained com pressor than one that has been rebuilt.)
REPLACING AN INOPERATIVE COMPRESSOR
com pressor to be replaced to effect oil return to
it the following will apply. DO NOT add any more
oil than is necessary as maximum cooling will be
reduced.
and measure the oil.
than 1-1/2 fluid ozs., subtract this amount drained
from the original oil charge of 11 ozs., to obtain
"oil loss." Take the new compressor assembly
and drain from it the amount of "oil loss" above;
provided the refrigeration system shows no evi­
If the system has been or can be operated for
After draining and measuring the oil from the
After idling com pressor (on vehicle) to be re­
1. Compressor replaced with service com ­
a. Remove compressor and place in a hori­
b. Drain oil from replacement com pressor and
c. (1) If amount of oil drained in'^"previous­
ly is more than 4 ozs., place into the
new compressor the same amount of oil
drained from the replaced com pressor.
(2) If amount of oil drained in "a"previous­
ly is le ss than 4 ozs., place 6 ozs. of
oil in the replacement com pressor.
d. Install com pressor.
2. Compressor replaced with a field repaired
a. Proceed as in step 1 previously, and then
In the case when it is not possible to idle the
1. Remove com pressor from vehicle, drain
2. If amount drained in step 1 above is more