General Repair Proceduces And Component Replacement - GMC 1976 ZEO 6083 Maintenance Manual

Figure 30-Adjusting Thermostatic Switch
change the outlet temperature approximately 4
degrees.
6. Reinstall switch end plate and reinstall switch .
Be sure that the air sensing capillary has been re-
placed properly .
7. Check system performance. If further adjust-
ment is needed, repeat Steps 3 through 6 until the
prescribed pressure is reached .
NOTE :
Do not attempt to run a Performance
Check with the system disassembled since inac-
curate readings would be the result. ALWAYS
reinstall switch and capillary and any duct work
before running a performance check .
EXPANSION VALVE (FIGURES 15
& 16)
A malfunction of the expansion valve will be
caused by one of the following conditions; valve
stuck open, valve stuck closed, broken power ele
ment, a restricted screen or an improperly located or
installed power element bulb .
Attachment of the expansion valve bulb to the
evaporator outlet pipe is very critical . The bulb must
be attached tightly to the pipe and must make good
PREPARING SYSTEM FOR
REPLACEMENT OF COMPONENT
PARTS
Air conditioning, like many other things, is fairly
AIR CONDITIONING SYSTEM
1- 6 3
contact with the pipe along the entire length of the
bulb . A loose bulb will result in high "high side"
pressures and poor cooling. On bulbs located outside
the evaporator case, insulation must be properly in-
stalled.
Indications of expansion valve trouble provided
by the Performance Test are as follows :
VALVE STUCK OPEN
Noisy Compressor .
No Cooling - Freeze Up.
VALVE STUCK CLOSED, PLUGGED
SCREEN OR BROKEN POWER ELEMENT
Very Low Suction Pressure.
No Cooling.
POORLY LOCATED POWER ELEMENT
BULB
Normal Pressure .
Poor Cooling.
CHECK FOR DEFECTIVE VALVE
The following procedure must be followed to de-
termine if a malfunction is due to a defective expan-
sion valve .
1 . Check to determine if the system will meet the
performance test as outlined previously . Ifthe expan-
sion valve is defective, the low pressure readings will
be above specification .
2. The loss of system performance is not as evi-
dent when the high side pressure is below 200 PSI.
Therefore, it may be necessary to increase the system
high side pressure by partially blocking the con-
denser . Disconnect the blower lead wire and repeat
the "Performance Check" to determine if the low
side pressure can be obtained .
GENERAL REPAIR PROCEDURES AND
COMPONENT REPLACEMENT
simple to service once it is understood . However,
there are certain procedures, practices and precau-
tions that should be followed . For this reason it is
strongly recommended that the preceding informa-
tion in this section be studied thoroughly before at-
tempting to service the system .