Condenser - GMC 1982 Light Duty Truck Service Manual

E X P A N S IO N TUBE (ORIFICE)
Rem oval a n d Installation
1. D ischarge the refrigerant from the system.
2. Disconnect liquid line at evaporator inlet and remove
expansion tube (orifice) from the inlet pipe.
3. To install, reverse the above procedure.
installing th e expansion tu b e (orifice) inside the
ev ap o ratio r inlet pipe, it M U S T be installed with
" shorter screen end " inserted first.
SPECIFIC C O M P O N E N T D IA G N O S IS
The following is a description of the type of symptom
each refrigerant component will evidence if a defect occurs:
COMPRESSOR
A com pressor defect will appear in one of four ways:
Noise, seizure, leakage, or low discharge pressure.
NOTICE: R esonant com pressor noises are not cause for
alarm ; however, irregular noise or rattles may indicate
broken parts or excessive clearances due to wear. To
check seizure, de-energize the m agnetic clutch and
check to see if drive plate can be rotated. If rotation is
im possible, com pressor is seized (R e fe r to "F alse
C om pressor S eizu re"). To check for a leak, refer to
leak testing. Low discharge pressure may be due to a
faulty internal seal of the com pressor, or a restriction in
the compressor.
NOTICE: Furtherm ore, low discharge pressure may be
due to an insufficient refrigerant charge or a restriction
elsewhere in the system. These possibilities should be
checked prior to servicing the com pressor. If the
com pressor is inoperative, but is not seized, check to see
if current is being supplied to the m agnetic clutch coil
term inals.
CO NDENSER
A condenser may be defective in two ways: it may leak,
or it m ay be restricted. A condenser restriction will result in
excessive com pressor d isch arg e pressure. If a p artia l
re stric tio n is present, som etim es ice or frost will form
im m ediately after the restriction as the refrigerant expands
after passing through the restriction. If air flow through the
condenser or radiator is blocked, high discharge pressures
will result. During normal condenser operation, the outlet
pipe will be slightly cooler than the inlet pipe.
RECEIVER-DEHYDRATOR - M O T O R H O M E
CHASSIS
A defective re ceiv er-d eh y d rato r m ay be due to a
restriction inside the body of the unit. A restriction at the
inlet to the receiv er-d eh y d rato r will cause high head
pressures. O utlet tube restrictions will be indicated by low
head pressures and little or no cooling. An excessively cold
receiver-dehydrator outlet may be indicative of a restriction.
E X P A N S IO N V A LV E
A m alfunction of the expansion valve will be caused by
one of the following conditions: valve stuck open, valve stuck
closed, broken power elem ent, a restricted screen or an
im properly located or installed power elem ent bulb. The
first three conditions require valve replacem ent. The last two
may be corrected by replacing the valve inlet screen and by
properly installing the power element bulb.
A tta c h m en t of the expansion valve bulb to the
evaporator outlet line is very critical. The bulb must be
attached tightly to the line and must make good contact
with the line along the entire length of the bulb. A loose bulb
W hen
will result in high low side pressures and poor cooling.
Indications of expansion valve trouble are provided by
perform ance tests; consult diagnostic charts.
1. VALVE ST U C K O PE N
a. Noisy Com pressor
b. No Cooling - Freeze Up.
2. Valve stuck closed, broken power elem ent or plugged
screen
a. Very Low Suction Pressure.
b. No Cooling.
3. PO O R L Y LO C A T E D PO W E R E L E M E N T BULB
a. N orm al Pressure.
b. Poor Cooling.
Diagnosis for Defective V alve
The following procedure m ust be followed to determ ine
if a m alfunction is due to a defective expansion valve.
1. C heck to d eterm in e if the system will m eet the
p erform ance test as outlined previously.
expansion valve is defective, the low pressure readings
(evaporator pressure) will be above specifications.
2. The loss of system perform ance is not as evident when
the compressor head pressure is below 1 379 kPa (200
psi). Therefore, it may be necessary to increase the
system head pressure by p artially blocking the
condenser. Disconnect the blower lead wire and repeat
the "p e rfo rm a n ce
evaporator pressure can be obtained.
3. The system will also indicate a low refrigerant charge
by bubbles occurring in the sight glass (M otor Home
Chassis System s).
EVAPO RATO R
W hen the evaporator is defective, the trouble will show
up as an inadequate supply of cool air. A partially plugged
core due to dirt, a cracked case, or a leaking seal will
generally be the cause.
REFRIGERANT LINE RESTRICTIONS
Restrictions in the refrigerant lines will be indicated as
follows:
1. Suction Line - A restricted suction line will cause low
suction pressure at the com pressor, low disch arg e
pressure and little or no cooling.
2. Discharge Line - A restriction in the discharge line
generally will cause the pressure relief valve to open.
3. Liquid Line - A liquid line restriction will be evidenced
by low discharge and suction pressure, and insufficient
cooling.
Sight Glass Diagnosis (M otor Hom e Chassis Units)
A t tem peratures higher than 70°F (21°C ), the sight
glass m ay indicate w heter the refrig eran t charge is
sufficient. A sh o rtag e of liquid refrig eran t is indicated
AIR CONDITIONING
If the
ch eck" to d eterm in e if the
IB-31