Chevrolet Light Duty Truck 1973 Service Manual page 108

INSUFFICIENT COOLING DIA GNO SIS CHART (EXCEPT C -K FOUR-SEASON SYSTEM)
The fo llo w in g procedures should be applied before perform ance testing an A/C System.
1. Check fo r proper belt installation and tension w ith J-23600.
2. Check fo r proper clutch coil terminal connector installation.
3. Check fo r clutch air Gap (.022 - .057).
4. Check fo r broken, burst, or cut hoses. Also check fo r loose fittin g s on all components.
NO RM AL A IR FLOW
| CHECK DISCH ARGE A IR TEM P ERATURE (SEE PERFORMANCE D A T A ) |
D ISCH ARG E TE M P ER ATU R E HIGH O U TLET AIR
A T O U T L E T COLD TEMPERATURE
CHECK FOR A IR LEAK S TH RO UG H DASH PANEL.
CHECK SIGHT GLASS
DOORS, WINDOWS, OR FROM HEATER .
| -
a m i n g
SYSTEM IS PR O B A B LY LOW ON R E FR IG E R A N T. 1. SYSTEM MAY BE EITH E R F U L L Y CHARG ED OR EM PTY.
CHECK FOR LEAK S, REPA IR , AN D ADD
R E F R IG E R A N T. IF FO AM IN G S T IL L OCCURS,
CHECK FOR RESTR IC TIO N IN R E FR IG E R A N T
2. IF PIPES ARE NOT IN D IC A T IN G PROPER TEM PERATURES,
SYSTEM BETW EEN CONDENSER A N D SIGHT
GLASS.
LOW EVAP O RATO R 'C H E C K EVAPORATOR PRESSURE
' PRESSURE
CHECK EVAP O R ATO R O U TLE T LINE
EVAP O RATO R O U TLET
L IN E W ARM
I CHECK COMPRESSOR DISCH ARG E PRESSURE
1. CHECK FOR L IQ U ID LIN E RESTRICTION
(FROST SPOT ON LIN E ). IF NOT,
2. CHECK FOR PLUGGED IN L E T SCREEN IN
EXPANSION V A L V E . IF NOT,
3. CHECK FOR D E FE C TIVE EXPANSION V A L V E
BY R EM O V IN G V A L V E AN D BLOW ING THRO UGH
V A L V E . IF U N A B LE TO BLO W THRO UGH V A LV E ,
BULB IS D ISC H ARG ED. REPLACE EXPANSION
V A L V E .
LOW DISCHARGE
I
* PRESSURE
Check fo r m alfunctioning
expansion valve-See
Component Diagnosis.
5. Check fo r condenser air blockage due to foreign material.
6. Check fo r proper air ducting hose connections.
7. Check heater temperature door adjustm ent, adjust if incorrect.
8. Check evaporator sealing fo r air leak, repair if leaking.
9. Install pressure gages and therm om eter and make performance test.
CHECK A IR FLOW
BLOWER NOT OPERATING
CHECK FOR BLOWN FUSE, D E FE C TIVE BLOW ER SWITCH,
BROKEN W IRE, LOOSE CONNECTIONS. LOOSE BLOWER MOTOR
GROUND W IRE OR IN O P E R A T IV E BLOWER MOTOR.
NO FO AM ING
FEEL HIGH AND LOW PRESSURE PIPES A T COMPRESSOR.
HIGH PRESSURE PIPE SHO U LD BE W ARM . LOW PRESSURE
PIPES SHOULD BE COLD.
RECHARGE SYSTEM AS RECO M M ENDED. IF N O ZZLE A IR
TEMPERATURE IS S T IL L HIG H . CHECK EVAP O RATO R
PRESSURE.
X
HIGH EVAP O RATO R
* PRESSURE I
HIG H DISCH ARGE PRESSURE
X
1. Check engine cooling system, fan clutch and check
fo r 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 diffe re n t, 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 outle t
air tem perature and compressor discharge
pressure w hile slowly discharging system at
receiver inlet connection.
Fig. 101-Insufficient Cooling Diagnosis-Except C-K Four-Season System
IN O OR LOW A IR FLOW
CHECK BLOWER OPERATIO N
)_ t
Check fo r loose or disconnected air distrib u tio n ducts,
restricted or leaking air ducts, partially closed air o u t­
let valve or clogged evaporator core, if above check is
OK, check for ice blocking evaporator.
ICE BLO C KIN G
EVAP O R ATO R
CHECK FOR LOW EVAP O R ATO R PRESSURE
1. A LLO W SYSTEM TO W ARM UP.
2. STOP A N D R ESTART ENGINE.
3. CHECK EVAP O R ATO R PRESSURE
IM M E D IA T E L Y A FTE R RESTART AN D
PULL DOWN OF EVAP O R ATO R PRESSURE.
N O R M A L EVAPO RATO R
PRESSURE
SYSTEM HAS EXCESS M O ISTURE. REPLACE RECEIVER
D E H Y D R A TO R A N D E V AC U ATE TH O R O U G H LY . RECHARGE
SYSTEM.
N O R M A L
EVAP O RATO R PRESSURE
| Check Compressor Discharge Pressure.
LOW DISCHARGE PRESSURE N O R M AL DISCH ARGE PRESSURE
Check for restriction in liquid line,
R efrigeration System is ok
p artia lly plugged inlet screen at
1. Check fo r proper fu n c tio n of heater TEM P ER ATU R E door.
expansion valve, or defective
2. Check fo r proper sealing of evaporator case.
expansion valve, replace valve if
3. Check fo r proper operation and seal around tem perature door.
defective. 4. Non-Foam ing 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 o il is a
slipping clutch or belt or broken belt. To remove excess oil
in system consult service manual.
' REFER TO PERFORM ANCE
C H A R T FOR CORRECT PRESSURES
NO R M A L BLOWER O PE R ATIO N | I
LOW EVAP O R ATO R
* PRESSURE
Check fo r m alfunctioning
expansion valve-See
Component Diagnosis.
X