Figure 13-21.Adding R-12 (low side) for system check.
Using the vacuum pump, draw the system down to at
least 29 inches of mercury at sea level and hold it there
for at least 30 to 45 minutes. This will remove all
moisture from the system.
As the system is being pumped down, the vacuum
should drop to the required inches of mercury. If it does
not drop, this is an indication of a leak. In which case,
you must recharge the system to detect the leak. After
you detect the leak, repair the damage and re-evacuate
Once the system is totally evacuated, again-close
both valves on the gauge manifold set-disconnect the
vacuum pump and connect the refrigerant source.
ATTENTION: Any oil lost during the discharge of
refrigerant must be replaced or damage to the
compressor will result.
ATTENTION: During discharge of an automotive
air-conditioning system, the vehicle engine must NOT
In the past, when a system was discharged before
disassembly, the standard practice was to vent the
refrigerant into the atmosphere. For environmental and
legal reasons, this is no longer permissible. The proper
procedure is to use a refrigerant recovery/recycling
device (fig. 13-18) and reuse the refrigerant. You are to
turn in excess used refrigerant to the defense recycling
and management office (DRMO) for proper disposal.
ATTENTION: Disposal instructions for
refrigerants may not be the same at different naval
stations. Before you take any action concerning R-12 or
any refrigerant, contact your supply department for
proper disposal instructions.
ADDING REFRIGERANT TO THE
Now that the system is pumped down, leave the
gauge manifold set attached and attach your refrigerant
source, as shown in figure 13-21. You are to take the
1. Loosen the center hose connection at the gauge
2. Open the can valve for several seconds to purge
air from the center hose.
3. Tighten the hose connection and close the can
4. Start the vehicle engine and operate the air
5. With the system operating, slowly open the
low-side manifold hand valve to allow refrigerant to
enter the system.
NOTE: The low side of the system is the suction
side, and the compressor will pull the refrigerant from
the can into the system.
6. With the container in an upright (vapor) position,
add the refrigerant until the sight glass clears or the test
set gauge readings are normal.
7. Rock the refrigerant can from side to side to
increase the flow of refrigerant into the system.
Never turn a can into a position where
liquid refrigerant will flow into the system.