Chevrolet 1977 light duty truck, Руководство по обслуживанию

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INSUFF ICIENT COOLING D IA GNO SIS CHART (EXCEPT C-K FOUR-SEASON SYSTEM)
The follow ing procedures should be applied before performance testing an A/C System.
1. Check for proper belt installation and tension w ith 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.
5. Check fo r condenser air blockage due to foreign material.
6. Check fo r proper air ducting hose connections.
7. Check heater temperature dour adjustment, adjust if incorrect.
8. Check evaporator sealing fo r air leak, repair if leaking.
9. Install pressure gages and thermometer and make performance test.
I NORMAL A IR FLOW
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I
CHECK A IR FLOW
CHECK DISCHARGE A IR TEMPERATURE (SEE PERFORMANCE DATA) 1
- IN O OR LOW A IR FLOW I
1
i :___
DISCHARGE TEMPERATURE
AT OUTLET COLD
HIGH OUTLET A IR
TEMPERATURE
OWER NOT OPERATING
1 _______
CHECK BLOWER OPERATION
JORMAL BLOWER OPERATION |
CHECK FOR BLOWN FUSE, DEFECTIVE BLOWER SWITCH,
BROKEN WIRE, LOOSE CONNECTIONS, LOOSE BLOWER MOTOR
GROUND WIRE OR INOPERATIVE BLOWER MOTOR.
CHECK FOR A IR LEAKS THROUGH DASH PANEL.
DOORS, WINDOWS, OR FROM HEATER.
CHECK SIGHT GLASS
Check fo r 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.
(
f o a m i n g
! "
ICE BLOCKING
EVAPORATOR
NO FOAMING
SYSTEM IS PROBABLY LOW ON REFRIGERANT.
CHECK FOR LEAKS, REPAIR, AND ADD
REFRIGERANT. IF FOAMING S TILL OCCURS,
CHECK FOR RESTRICTION IN REFRIGERANT
SYSTEM BETWEEN CONDENSER AND SIGHT
GLASS.
, SYSTEM MAY BE EITHER FU L L Y CHARGED OR FMPTY.
FEEL HIGH AND LOW PRESSURE PIPES AT COMPRESSOR.
HIGH PRESSURE PIPE SHOULD BE WARM. LOW PRESSURE
PIPES SHOULD BE COLD.
. IF PIPES ARE NOT INDICATING PROPER TEMPERATURES,
RECHARGE SYSTEM AS RECOMMENDED. IF NOZZLE AIR
TEMPERATURE IS S TILL HIGH. CHECK EVAPORATOR
PRESSURE.
LOW EVAPORATOR
•PRESSURE
~T~
CHECK FOR LOW EVAPORATOR PRESSURE
1. ALLOW SYSTEM TO WARM UP.
2. S10P ANU RESTART ENGINE.
3. CHECK EVAPORATOR PRESSURE
IM M E D IA TE LY AFTER RESTART AND
PULL DOWN OF EVAPORATOR PRESSURE.
NORMAL EVAPORATOR
PRESSURE
‘ CHECK EVAPORATOR PRESSURE!
CHECK EVAPORATOR OUTLET LINE
EVAPORATOR OUTLET
LINE WARM
HIGH EVAPORATOR
*
PRESSURE
SYSTEM HAS EXCESS MOISTURE. REPLACE RECEIVER
UEHYDRATOR AND EVACUATE THOROUGHLY. RECHARGE
SYSTEM.
CHECK COMPRESSOR DISCHARGE PRESSURE
NORMAL
EVAPORATOR PRESSURE
LOW EVAPORATOR
* PRESSURE
Check fo r malfunctioning
expansion valve-See
Component Diagnosis.
1. CHECK FOR LIQ UID LINE RESTRICTION
(FROST SPOT ON LINE). IF NOT,
2. CHECK FOR PLUGGED INLET SCREEN IN
EXPANSION V ALV E. IF NOT,
3. CHECK FOR DEFECTIVE EXPANSION V ALV E
BY REMOVING VALV E AND BLOWING THROUGH
V A L V E . IF U N A B IF TO RLOW THROUGH V A LV E .
BULB IS DISCHARGED. REPLACE EXPANSION
V ALVE.
| Check Compressor Discharge Pressure. I
* | HIGH DISCHARGE PRESSURE |
LOW DISCHARGE
* PRESSURE
Check fo r malfunctioning
expansion valve-See
Component Diagnosis.
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 tor refrigerant restriction in condenser.
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.
| LOW DISCHARGE PRESSURE
\
Check for restriction in liquid line,
partially plugged inlet screen at
expansion valve, or defective
expansion valve, replace valve if
defective.
- I NORMAL DISCHARGE PRESSURE I
i ' —
r _ _ .
Refrigeration System is ok
1. Check for proper function of heater TEMPERATURE door.
L
Check fo r proper sealing of evaporator case.
3. Check fo r 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 "CHECKING COMPRESSOR OIL CHARGE".
•REFER TO PERFORMANCE
CHART FOR CORRECT PRESSURES
OUTLET AIR TEMPERATURE
DROPS AS COMPRESSOR
DISCHARGE PRESSURE DROPS
i ...............
LEAK TEST SYSTEM, REPAIR
AS NECESSARY, DISCHARGE,
EVACUATE, AND RECHARGE.
OUTLET A IR TEMPERATURE
INCREASES AS COMPRESSOR
DISCHARGE PRESSURE DROPS
REPLACE EXPANSION VALVE
NOTE: G-MODELS, Insufficient cooling, or too much cooling may
be the result of a potentiometer out of calibration; see "A m p lifie r
Board Potentiometer Adjustm ent" in the Maintenance and Adjust­
ment portion of this section.
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