Evacuating and Charging the AC System
2. Connect the center service hose from the gauge set to the
refrigerant container dispensing valve. Purge the hose of any
air using refrigerant gas pressure from the container.
3. Run the engine at 1200 to 1500 RPM, with the AC unit on
4. Open the dispensing valve, then the low side hand valve on
the manifold. Figure 9-5 illustrates system charging with
refrigerant gas entering the compressor on the suction (low
pressure) side of the system.
If there are no manufacturer's charging specifications,
you can watch the sight glass first for bubbles, then
In this illustration, refriger-
ant is added on the low side
ofthe system as a gas. The
engine must be running at
1200 to 1500 RPM to draw
the gas in.
5. Check the sight glass when you have added nearly the speci-
fied amount of refrigerant. Keep adding refrigerant until the
sight glass clears or you have added the specified refrigerant
charge. Use an oil injector to replace oil drained from the
system. Remember, a large leak may have resulted in nearly
all the lubricant being lost.
6. Close the valve on the refrigerant container. Close the hand
valve on the gauge set and check the gauge readings. The
gauges should read in the normal range.
7. Turn off the engine and AC system. Check for leaks. If the
system checks out OK, back seat the service valves. Remove
the manifold gauge set hose fittings from the compressor. If
Schrader valves are in use, be sure to remove the manifold
hose fittings quickly and carefully, using a glove or shop towel
to protect your hand. Replace the protective caps on the
compressor service valves.