Chevrolet Light Duty Truck 1973 Service Manual page 73

vacuum reduces, it indicates a leak in the system or
gauge connections; locate and repair all leaks.
Charging the System
1. Only after evacuating as above, is system ready for
charging. Note reading on sight glass of charging
cylinder. If it does not contain a sufficient amount
of refrigerant for a full charge, fill to the proper
level.
2. With High and Low Pressure Valves (1 and 2) open,
close Vacuum Control Valve (3), turn off vacuum
pump, open refrigerant control valve (4) and allow
refrigerant to enter system.
NOTE: If the charge will not transfer
completely from the station to the system,
close the high pressure valve at the gauge set,
set the air conditioning controls for cooling,
check that the engine com partment is clear of
obstructions, and start the engine. Compres­
sor operation will decrease the low side
pressure in the system.
System is now charged and should be checked as
outlined below:
Checking System Operation
1. Operate system for a maximum of five minutes at
maximum cooling, high blower speed and with
engine operating at 2000 RPM (exhaust should be
vented if inside).
2. When system is stabilized, the pressure gauges on
J - 2 4 0 9 5
TO LOW
PRESSURE
FITTING
CHARGING STATION
HIGH PRESSURE LINE
TO HIGH
PRESSURE
FITTING
Fig. 51-Adding Refrigeration Oil Using Tool J-24095
HEATER A N D AIR C O N D IT IO N IN G
the charging station should read pressures corre­
sponding to values listed under PERFORMANCE
DATA.
3. When correct system pressures are observed, check
system charge as described under "Refrigerant
Quick Check Procedure".
4. Feel outlet air distribution to ensure that cold air is
being distributed.
5. Disconnect gauge lines and cap fittings.
CAU TIO N:
fittings, be sure to remove the adapters from the
fittings rather than the gauge lines from the
adapters.
PERFORMANCE TEST
Under normal circumstances, it will not be necessary to
Performance Test a system as outlined below; however,
in certain instances, the following procedure may be
advantageous in diagnosing system malfunction.
The following fixed conditions must be adhered to in
order to make it possible to compare the performance of
the system being tested with the standards below:
1. Doors and windows closed. (Vehicle inside or in
shade.)
2. Hood up and engine exhaust suitably ventilated.
3. Vehicle in NEUTRAL with engine running at 2000
rpm.
4. Air Conditioning controls set for -
• Maximum cooling.
• High blower speed
5. TEMP control set at "CO LD " and all air
conditioning outlets open.
6. Gauge set installed.
7. System settled out (run-in approxim ately 10
minutes).
8. A thermometer placed in front of vehicle grille and
another in the right hand diffuser outlet.
NOTE: On Overhead Systems, place a third
thermometer in the rear unit center outlet.
9. An 18" fan placed in front of the vehicle and
blowing into the condenser.
REFRIGERANT
NOTE: Higher temperatures and pressures
OIL
will occur at higher ambient temperatures. In
areas of high humidity it is possible to have
thermometer and gauge readings approach
but not reach the figures listed in the
performance tables and still have a satisfac­
tory operating unit. However, it is im portant
to remember that low pressure has a direct
relationship to nozzle outlet temperature. If
pressure is too low, ice will gradually form on
the evaporator fins, restricting air flow into
When removing gauge lines from
LIGHT DUTY TRUCK SERVICE MANUAL
1A-47