14-27.1. AIR-CONDITIONING SYSTEM SERVICING (R-134a) (Cont'd)
e. Evacuating System
Never attempt to evacuate A/C system if system has not been
Discharge A/C system (refer to task c.) and flush A/C system if necessary (refer to task d.).
Connect manifold gauge set (3) to service ports (refer to task a.).
Connect vacuum pump to center hose (4) on manifold gauge set (3).
Turn vacuum pump on and open high-pressure gauge valve (2) and low-pressure gauge valve (1) on
manifold gauge set (3).
High-pressure side gauge should drop to zero or below. If not, a
blockage in A/C system is indicated.
Evacuate unit until low-pressure gauge reads 29 in. Hg of vacuum.
Continue evacuation for forty-five minutes after correct gauge reading of 29 in. Hg of vacuum has
Turn high-pressure gauge valve (2) and low-pressure gauge valve (1) on manifold gauge set (3) to
closed position after evacuation is complete.
Turn off vacuum pump and disconnect center hose (4) from vacuum pump.
Vacuum of 29 in. Hg should be sustained on low-pressure gauge
for at least ten minutes. If not, a leak in A/C system is indicated.
Identify source of leak and repair as necessary.
Check for leaks ten minutes after gauge valves are turned off.
Manifold gauge set can remain connected and service valves left
in mid-position if charging A/C system will follow immediately.
Disconnect manifold gauge set (3) (refer to task b.).