15-3. AIR CONDITIONING SYSTEM SERVICING (CONT)
d. Evacuating System.
Never attempt to evacuate A/C
system if system has not been
Discharge A/C system (refer to task c.).
Connect manifold gage set (refer to task
a.) to service valve ports (5) and (6).
Connect vacuum pump to center hose (4)
on manifold gage set (3).
Turn vacuum pump on and open low
pressure gage valve (1) and high pressure
gage valve (2) on manifold gage set (3).
· High side gage should drop to
"zero" or below. If not, a blockage
in A/C system is indicated.
· 29-30 pounds of vacuum should
be sustained on low pressure
gage for at least ten minutes. If
not, a leak in A/C system is
indicated. Identify source of leak
and repair as necessary.
Evacuate unit until low pressure gage
reads 29-30 pounds vacuum.
Continue evacuation for forty-five
minutes after correct gage reading of 29-
30 pounds vacuum has been achieved.
Turn low pressure gage valve (1) and high pressure gage valve (2) on manifold gage set
(3) to closed position after evacuation is complete.
Turn off vacuum pump and disconnect center hose (4) from vacuum pump.
Manifold gage set can remain connected if charging A/C system will follow immediately.
Disconnect manifold gage set (refer to task b.) from service valve ports (5) and (6).