GMC 1982 Light Duty Truck Service Manual page 59

The follow ing procedures should be applied before performance testing an A/C System,
t. Check for proper belt installation and tension w ith J-23600.
2. Check for proper clutch coil terminal connector installation.
3. Check fo r clutch air Gap (.022 - .057).
4. Check for broken, burst, or cut hoses. Also check for loose fittings on all components.
NO RM AL A IR FLOW
CHECK DISCHARGE AIR TEM P ERATURE (SEE PERFORMANCE D ATA)
DISCHARGE TEM PERATURE
AT O UTLET COLO
CHECK FOR A IR LEAKS THRO UGH DASH PANEL.
CHECK SIGHT GLASS
DOORS, WINDOWS, OR FROM HEATER.
( H
f o a m i n g
SYSTEM IS PROBABLY LOW ON REFR IG ER AN T.
CHECK FOR LEAKS, REPAIR, AND ADD
REFR IG ER AN T. IF FOAM ING S T IL L OCCURS,
CHECK FOR RESTRICTION IN R EFRIG ERANT
SYSTEM BETWEEN CONOENSER AND SIGHT
GLASS.
LOW EVAPORATOR •CHECK EVAPORATOR PRESSURE
•PRESSURE
~ ~ I ~
CHECK EVAPORATOR O UTLET LINE
EVAPORATOR OUTLET
LINE WARM
1. CHECK FOR L IQ U ID LINE RESTRICTION
(FROST SPOT ON LIN E ). IF NOT,
2. CHECK FOR PLUGGED IN LE T SCREEN IN
EXPANSION V A L V E . IF NOT,
3. CHECK FOR DEFECTIVE EXPANSION V A LV E
BY REM O VING V A LV E ANO BLOWING THROUGH
V A LV E . IF UNAB LE TO BLOW THROUGH V A L V E ,
BULB IS DISCHARGED. REPLACE EXPANSION
V A LV E .
LOW DISCHARGE
* PRESSURE
Check fo r m alfunctioning
expansion valve-See
Component Diagnosis.
•R EFER TO PERFORMANCE
CHART FOR CORRECT PRESSURES
I N S U F F I C I E N T C O O L I NG D I A G N O S I S C H A R T
D A S H M O U N T E D U N IT (M O T O R H O M E C H A S S IS U N IT S )
CHECK A IR FLOW
CHECK FOR BLOWN FUSE, D EFE CTIVE BLOWER SWITCH,
HIGH OUTLET AIR
BROKEN WIRE, LOOSE CONNECTIONS, LOOSE BLOWER MOTOR
TEMPERATURE
GROUND WIRE OR IN O P ER ATIVE BLOWER MOTOR.
NO FOAMING
1. SYSTEM M AY BE EITHER F U LL Y CHARGED OR EMPTY.
FEEL HIGH AN D LOW PRESSURE PIPES AT COMPRESSOR.
HIGH PRESSURE PIPE SHOULD BE W ARM . LOW PRESSURE
PIPES SHOULD BE COLD.
2. IF PIPES ARE NOT IN D IC A TIN G PROPER TEMPERATURES,
RECHARGE SYSTEM AS RECOMMENDED. IF NOZZLE AIR
TEM PERATURE IS S T IL L HIGH. CHECK EVAPORATOR
PRESSURE.
X
X
X
HIGH EVAPORATOR
* PRESSURE
—
1
CHECK COMPRESSOR DISCHARGE PRESSURE
HIGH DISCHARGE PRESSURE
X
1. Check engine cooling system, fan clutch and check
for restricted air flo w thru condenser.
2. Check expansion valve bulb contact. Correct if
necessary.
3. Check fo r refrigerant restriction in condenser.
Return bends at equal elevation should be
approxim ately same temperature. If temperature
of bends is appreciably different, the cooler
bend indicates a restricted circuit, replace con­
denser if restriction is found, If condenser is OK,
check fo r air in system. To check observe outlet
air temperature and compressor discharge
pressure while slowly discharging system at
receiver inlet connection.
OUTLET A IR TEMPERATURE
OROPS AS COMPRESSOR
DISCHARGE PRESSURE DROPS
I
LEAK TEST SYSTEM, REPAIR
AS NECESSARY, DISCHARGE,
EVAC UATE, AND RECHARGE.
5. Check fo r condenser air blockage due to foreign material.
6. Check for proper air ducting hose connections.
7. Check heater temperature door adjustment, adjust if incorrect.
8. Check evaporator sealing for air leak, repair if leaking.
9. Install pressure gages and thermometer and make performance test.
IN O OR LOW AIR FLOW
CHECK BLOWER OPERATION
BLOWER NOT OPERATING
Check fo r loose or disconnected air distribution ducts,
restricted or leaking air ducts, partially closed air ou t­
let valve or clogged evaporator core, if above check is
OK, check for ice blocking evaporator.
CHECK FOR LOW EVAPORATOR PRESSURE
1. ALLO W SYSTEM TO WARM UP.
2. STOP ANO RESTART ENGINE.
3. CHECK EVAPORATOR PRESSURE
IM M E D IA T E LY AFTER RESTART AND
PULL DOWN OF EVAPORATOR PRESSURE.
NORM AL EVAPORATOR
PRESSURE
SYSTEM HAS EXCESS MOISTURE. REPLACE RECEIVER
DEH Y D R A TO R ANO EVACUATE THOR OUGHLY. RECHARGE
SYSTEM.
NORMAL
EVAPORATOR PRESSURE
T
| Check Compressor Discharge Pressure
(L O W DISCHARGE PRESSUREj T NORM AL DISCHARGE PRESSURE
Check for restriction in liquid line,
Refrigeration System is ok
p artia lly plugged inlet screen at
1. Check for proper function of heater TEMPERATURE door.
expansion valve, or defective
2. Check for proper sealing of evaporator case.
expansion valve, replace valve if 3. Check for proper operation and seal around temperature door.
defective. 4. Non-Foaming sight glass does not always indicate a fu lly
charged system. Add 1/2 lb. refrigerant and observe
performance.
5. Check fo r excess oil in system. A sym ptom of excess oil is a
slipping clutch or belt or broken belt. To remove excess oil
in system see "C H EC K IN G COMPRESSOR OIL CHARG E".
Dash M ou n te d U n it (M o to r H om e Chassis)
(R e frig e ra n t Cha ge - - 3 lbs 4
T em p eratu re o f
Air E n tering
C on den ser
O U TLET A IR TEMPERATURE
E ngine rpm
INCREASES AS COMP! ~ "? R
DISCHARGE PRESSURE DROPS
C o m p resso r
Head Pressure*
REPLACE EXPANSION VALVE
D ischarge Air
T e m p eratu re *
•Ju « t p rio r to c o m p re sso r c lu tc h d isen gagem en t
FORMAL BLOWER OPERATION |
X
ICE BLOCKING
EVAPORATOR
LOW EVAPORATOR
[ L
* PRESSURE
Check fo r malfunctioning
expansion valve-See
Component Diagnosis.
I ,J
*.)
70° 80° 90° 100° 110° 120°
2000
1 1 0 -
135 - 160- 190- 220- 260-
120 M S 170
200 230 270
9 10 13
10
40- 41- 41- 4 2 - 44 44
45 46 46 47 49 49