Do not evacuate before recovering
refrigerant in A/C system.
Once air conditioning system circuit is
opened (exposed) to atmospheric air, system
must be evacuated by using a vacuum pump.
The A/C system should be attached with a
manifold gauge set, and should be evacuated
for approximately 15 minutes.
1) Connect high charging hose (1) and low charging
hose (2) of manifold gauge set (3) (special tool)
respectively as follows:
High charging hose → High pressure charging valve
(4) on discharge hose
Low charging hose → Low pressure charging valve
(5) on suction pipe
2) Attach center charging hose (6) of manifold gauge
set to vacuum pump (7).
3) Operate vacuum pump, and then open discharge
side valve (Hi) (8) of manifold gauge set.
If there is no blockage in the system, there will be an
indication on high pressure gauge (9).
When this occurs, open the other side valve (Lo)
(10) of the set.
4) Approximately 10 minutes later, low pressure gauge
(11) should show a vacuum lower than –100 kPa (–
, –760 mmHg, –14.7 psi) providing no
• If the system does not show a vacuum
below –100 kPa (–1.0 kgf/cm
–14.7 psi), close both valves, stop vacuum
pump and watch movement of low
• Increase in the gauge reading suggests
existence of leakage. In this case, repair
the system before continuing its
• If the gauge shows a stable reading
(suggesting no leakage), continue
Checking A/C System for Pressure Leaks
After completing the evacuation, close manifold gauge
high pressure valve and low pressure valve and wait 10
minutes. Verify that low pressure gauge reading has not
, –760 mmHg,
Air Conditioning System: Manual Type 7B-19
5) Evacuation should be carried out for a total of at
least 15 minutes.
6) Continue evacuation until low pressure gauge
indicates a vacuum less than –100 kPa (–1.0 kgf/
, –760 mmHg, –14.7 psi), and then close both
7) Stop vacuum pump. Disconnect center charging
hose from pump inlet. Now, the system is ready for
If the gauge reading moves closer to "0",
there is a leak somewhere. Inspect the tubing
connections and make necessary
corrections. And then, evacuate system once
again and make sure that there are no leaks.