GMC 1976 ZEO 6083 Maintenance Manual page 753

24E- 14
ROOF MOUNTED AIR CONDITIONER
Figure 1 7-Breaking into the Refrigeration System
(Typical)
CAPILLARY TUBE
Never try to repair the capillary tube . It is a
metering device and the length and diameter are
critical . Install a new tube that exactly duplicates the
original . Avoid using too much solder since the open
end could be easily plugged .
SAFETY VALVE-DUO THERM
The rectangular piece soldered on the suction
line as it comes out of the evaporator is not a patch
to cover up an accident .
The patch was soldered in place with a soft solder
that will melt in case of fire allowing the refrigerant
to escape before the system pressure becomes dan-
gerously high .
COMPRESSOR
The replacement of a compressor because of me-
chanical failure or very mild electrical burnout is a
simple operation.
A severe electrical burnout however usually cre-
ates an acid condition throughout the system . If all
the acid and other contaminates are not removed the
new compressor will be short lived .
A severe burnout will usually be indicated by a
characteristic odor of burned insulation when the
system is opened . If there is any doubt about the
burnout, pour some oil out of the compressor into a
shallow pan for observation and testing.
WARNING : DO NOT TOUCH THE OIL WITH
YOUR HANDS IF THERE IS A BURNT SMELL, IT
MAY HAVE FORMED ACID .
If the oil is clear and free of odor the system is
probably free of contamination. If the oil is dark and
has an odor, acid has probably formed in the system .
The use of an acid test kit will give you a positive
indication of the system condition.
If the system is contaminated discharge all refrig-
erant from the system . Remove burned compressor,
capillary tube and drier. While the system is open
flush it, in reverse of normal flow pattern, with either
a pound of refrigerant 22 or use "Purge" or equiva-
lent followed by a brief flush of 22 .
If the system has been contaminated to the extent
that solids have been formed it is a good idea to tie
a cloth over one of the open ends to catch the
material blown out. This will give you a visual indi-
cation if further flushing is necessary.
If the original cap tubes are open they can be
reinstalled . If plugged they should be replaced . In-
stall replacement compressor, the filter at the outlet
of the condenser and the filter-dryer in the suction
line between the compressor and evaporator . Install
process tube with charging port at the compressor .
Install the charging port in tubing of sufficient
length so it can be removed after evacuation, re-
charging and leak testing. This will give the customer
a hermetically sealed system and one you can be
confident will be performing as originally designed .
If the compressor failure was caused by a me-
chanical failure or if no acid was found when you
tested the original oil the flushing operation can be
omitted. Most failures are of this nature .
Systems that are contaminated to the point solids
have been formed are usually caused by poor prior
service where air and/or acids have been left in the
system from incomplete evacuation and cleanup.
EVACUATING AND CHARGING
SYSTEM (FIGURE 18)
1. Connect a vacuum pump to the manifold .
Purge the vacuum hose of charging station (J-24410)
before starting the pump . If you have a micron type
vacuum pump, run it until the gauge reads 200 to 500
microns. This may take some time, since all the mois-
ture has to boil before the gauge will read . With an
automotive pump, pull the system down to about
29-1/2 inches or as close to it as the system will go .