When finished with any system, remove gauges as follows.
1. With unit running, close (back-seat) the "high-side" service valve if so equipped.
2. Remove "high-side" hose, and connect to holder.
3. Charging or center hose connected to holder
4. Open "high-side" hand wheel on gauge manifold
5. Open "low-side" hand wheel on gauge manifold allowing the refrigerant to be pulled into the "low-side" or suction side of compressor.
6. Close both hand wheels on gauge manifold.
7. "Back-Seat" suction service valve if so equipped
8. Remove "low-side" hose.
9. Replace all caps'
By using this method you leave the refrigerant in the unit. This is espceilly important with "critical-charged" units.