AC retrofit: how to find a leak?

[Konstantin Bogach]

Hi.
After 2 month break I resumed working on it.  I connected all together,
pumped vacuum,  closed gauge manifold valves and found that pressure
raised from 28 mmHg to 12 mmHg within a half an hour.   Is there a DIY
method of leak detection without refrigerant in the system?

O-ring are new, green and I tighten all connections.  I use old low
pressure hose and new, manufactured by local AC shop,  high pressure
hose.


Thanks.
Konstantin Bogach.