Evacuating and charging the air conditioning system is a combined procedure
in which the lines are purged, then refrigerant is added to the system in proper
quantity. Charging is always conducted through the low pressure fitting. NEVER attempt
to charge the air conditioner through the high pressure side of the system.
If a charging station and pump is available, the following general procedures
should be observed, in addition to the operating instructions provided by the
manufacturer.
- The proper amount of fresh compressor oil must be added to the system before
charging. This can be accomplished by disconnecting the suction hose and pouring
the fresh oil into the hose or pipe and then reconnecting the system.
- Properly connect a manifold gauge set to the vehicle, then connect the center
manifold gauge hose to a vacuum pump.
- Turn the vacuum pump ON and slowly open the high and the
low side valves to the pump. Allow the system to evacuate for 25–30
minutes, then note the gauge readings. If the system is unable to reach 28–29
in. Hg (193–199 kPa), of vacuum, the system and vacuum pump must be
checked for leaks and repaired before proceeding further.
- After the system has been evacuated for at least 25 minutes, close the gauge
high and low side valves then shut the pump OFF.
- Watch the low side gauge for vacuum loss. If vacuum loss is in excess of
1 in. Hg (3 kPa), then leak test the system, repair the leaks and return to
Step 1. Before leak testing, remember to disconnect the gauge high side connector
from the service port.
- If after 1–3 minutes, the loss is less than 1 in. Hg (3 kPa), then
proceed with the system charging.
- Disconnect the gauge high side connection from the service port and the
hose from the vacuum pump.
- Engage the center manifold connection to an R–12 source. If you are
using a refrigerant drum instead of a charging station, place the drum on
a scale to determine the amount of refrigerant being used.
- Open the source and the low side gauge valve, then monitor the weight of
the drum or the rate at which the charging system is introducing the R–12
into the system.
- When 1 lb. (0.454 Kg) of R–12 has been added to the system, start
the engine and turn the air conditioning system ON. Set the temperature
level to full cold, the blower speed on high and the selector lever to the
dash outlets. Under this condition, slowly draw in the remainder of the R–12
charge. The proper amount can be found on a label either on the compressor
or on the evaporator case on the firewall.
- When the system is charged, turn the source valve OFF and
continue to run the engine for 30 seconds in order to clear the gauges and
the lines
- With the engine still running, carefully remove the gauge low side hose
from the suction service fitting. Unscrew the connection rapidly to avoid
excess refrigerant loss.
CAUTION
If the hoses of the manifold gauge set can be disconnected from the gauge,
NEVER remove a hose from the gauge while the other end of the hose is still
connected to the service port. Since the service valve fitting check valve
is depressed by the hose connection, this would cause a complete and uncontrolled
discharge of the system. Serious personal injury could be caused by the
escaping R–12.
- Install the protective service fitting caps and hand-tighten.
- Turn the engine and air conditioning OFF.
- If an electronic or halide leak tester is available, test the system for
leaks.
- If there are no leaks, perform the refrigerant level test to verify proper
system charging.
