Chevrolet 1980 Light Duty Truck Service Manual page 63

The following procedures should be applied before performance testing an A/C System.
1. Check for proper belt installation and tension with J-23600.
2. Check for proper clutch coil terminal connector installation.
3. Check for clutch air Gap (.022 - .057).
4. Check for broken, burst, or cut hoses. Also check for loose fittings on all components.
NORMAL A IR FLOW
CHECK DISCH ARGE AIR TE M P ER A TU R E (SEE PERFO RM AN CE DATA)
DISC H ARG E T EM P ER A TU R E HIGH O U TLET A IR
A T O U TLET COLD TE M P ER A TU R E
CH ECK FOR A IR LE A K S THROUGH DASH PANEL.
| CH ECK SIG H T GLASS |
DOORS, WINDOWS, OR FROM H E A TE R .
| f o a m in g | "
SYSTEM IS PR O B A BLY LOW ON R EF R IG E R A N T . 1. SYSTEM MAY BE E IT H E R F U L L Y C H ARG ED OR EM PTY.
CH ECK FOR L E A K S , R EP A IR , AND ADD F E E L HIGH AND LOW PR ESSU R E PIPES A T COMPRESSOR.
R E F R IG E R A N T . IF FOAMING S T IL L OCCURS, HIGH PR ESSU R E PIPE SHOULD BE WARM. LOW PR ESSU R E
PIPES SHOULD BE COLD.
CH ECK FOR R ESTR IC TIO N IN R E F R IG E R A N T
SYSTEM BETW EEN CONDENSER AND SIGHT 2. IF PIPES A R E NOT INDICATING PROPER TE M P ER A TU R ES ,
R EC H A R G E SYSTEM AS RECOM MENDED. IF NOZZLE AIR
GLASS.
TE M P ER A TU R E IS S T IL L HIGH. CHECK EVAPO RA TO R
P R ES SU R E.
LOW EVAPO RATO R 'C H E C K EVAPO RA TO R PR ESSU R E
•PRESSU R E
CH ECK EVAPO RATO R O U TLET LINE
EVAPO RATO R O U TLET
LIN E WARM
CH ECK COMPRESSOR DISCH ARG E PRESSU RE
1. CH ECK FOR LIQUID LINE RESTRICTIO N
(FR O ST SPOT ON L IN E ). IF NOT,
2. CH ECK FOR PLUGGED IN LE T SCREEN IN
EXPANSION V A L V E . IF NOT,
3. CH ECK FOR D E F EC T IV E EXPANSION V A LV E
BY REM OVING V A L V E AND BLOWING THROUGH
V A L V E . IF UN ABLE TO BLOW THROUGH V A L V E ,
BU LB IS DISCH ARG ED. R EP LA C E EXPANSION
V A L V E .
LOW DISCHARGE
* PR ESSU R E
Check for malfunctioning
expansion valve-See
Component Diagnosis.
• R E F E R TO PERFORM ANCE
C H ART FOR C O RRECT PRESSURES
INSUFFICIENT COOLING DIAGNOSIS CHART
DASH M OUNTED UNIT (MOTOR HOME CHASSIS UNITS)
5. Check for 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.
^ nsta^ Pressure gages and thermometer and make performance test.
CHECK A IR FLOW
BLOWER NOT OPERATING
CH ECK FOR BLOWN FU SE, D E F E C T IV E BLO W ER SWITCH,
BRO KEN W IRE, LOOSE CONNECTIONS, LOOSE BLO W ER MOTOR
GROUND W IRE OR IN O P ER A TIV E BLOW ER MOTOR.
I
NO FOAMING
x
SYSTEM HAS E X C ESS M O ISTU RE. R EP LA C E R E C E IV E R
SYSTEM .
HIGH EVAPO RA TO R
* PR ESSU R E
HIGH DISCH ARG E PR ESSU R E
X
1. Check engine cooling system, fan clutch and check Check for restriction in liquid line,
for restricted air flow thru condenser.
partially plugged inlet screen at
2. Check expansion valve bulb contact. Correct if
expansion valve, or defective
necessary.
expansion valve, replace valve if
3. Check for refrigerant restriction in condenser.
defective.
Return bends at equal elevation should be
approximately 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 for air in system. To check observe outlet
air temperature and compressor discharge
pressure while slowly discharging system at
receiver inlet connection.
O U TLET A IR TE M P ER A TU R E
DROPS AS COMPRESSOR
D ISCH ARG E PR ESSU R E DROPS
DISCH ARG E PR ESSU R E DROPS
L -. i — ...~
LE A K T E S T SYS TEM , R EP A IR
AS N EC E SSA R Y , D ISC H A R G E,
E V A C U A T E . AND R EC H A R G E .
INO OR LOW A IR FLOW
CHECK BLOWER OPERATION
NORMAL BLOW ER OPERATIO N
Check for loose or disconnected air distribution ducts,
restricted or leaking air ducts, partially closed air out­
let valve or clogged evaporator core, if above check is
OK, check for ice blocking evaporator.
----------------------
ICE BLO CKIN G
EVAPO RA TO R
CHECK FOR LOW EVAPO RA TO R PR ESSU R E
1. ALLOW SYSTEM TO WARM UP.
2. STOP AND R E S T A R T ENGINE.
3. CHECK EVAPO RA TO R PR ESSU R E
IM M ED IA TELY A F T E R R E S T A R T AND
PU LL DOWN OF EVA PO RA TO R P R ES SU R E.
N O R M A L.EVA PO RA TO R
PR ESSU R E
O EH YD R A TO R AND EV A C U A T E TH O R O U G H LY . R EC H A R G E
NORMAL
EVAPO RA TO R PR ESSU R E
X
| Check Compressor Discharge Pressure.
LOW DISCHARGE P R E S S U R E ! NORMAL DISCHARG E PR ESSU R E
X
Refrigeration System is ok
1. Check for proper function of heater TE M P ER A TU R E door.
2. Check for proper sealing of evaporator case.
3. Check for proper operation and seal around temperature door.
4. Non-Foaming sight glass does not always indicate a fully
charged system. Add 1/2 lb. refrigerant and observe
performance.
5. Check for excess oil in system. A symptom of excess oil is a
slipping clutch or belt or broken belt. To remove excess oil
in system see "C H EC KIN G COMPRESSOR OIL C H A R G E".
Dash M ounted U n it (M o to r Hom e Chassis)
(Refrigerant Charge — 3 lbs.- 4 oz.)
Temperature of
Air Entering 70°
Condenser
O U T L ET A IR T EM PER A TU R E Engine rpm
IN C R EA SES AS COMPI ' " ? R
Compressor 110-
Head Pressure* 120
Suction
R EP LA C E EXPANSION V A L V E
6
Pressure psi*
Discharge Air
40-
Temperature*
45
•Just prior to compressor clutch'disengagement.
-------------
LOW EVA PO RA TO R
( l i
* PR ESSU R E
Check for malfunctioning
expansion valve-See
Component Diagnosis.
80° 90° 100° 110° 120°
2000
135- 160- 190- 220- 260-
145 170 200 230 270
7 9 10 10 13
41- 41- 42- 44- 44-
46 46 47 49 49