The A18-5300 uses a 4 way Manifold A18-5087 that has the “Normal” 2 taps for the High and Low side of the A/C system.
The Other 2 taps are:
Black – Vac - Vacuum, this tap is to be connected to the inlet of the vacuum pump for evacuation. Closing this tap disconnects this line from the central manifold passage.
Yellow – REF – Refrigerant, This tap can be initially connected to the inlet of the recovery unit with the outlet of the reclaim machine connected to the recovery bottle. Once recovery has been completed and the manifold set shows a negative pressure this hose can be disconnected and connected to the fresh refrigerant cylinder in readiness for refilling the system. This yellow hose has a ball valve fitted to minimise refrigerant loss from the hose as it is disconnected from the fresh cylinder. This also enables the remaining refrigerant in the yellow hose to be reclaimed.
Opening any of these taps connects the various lines connected to them to a central manifold passage. Closing the Red and Blue taps closes them to the central manifold passage but still leaves the gauges connected to their relevant hoses to show pressures in the system for diagnosis.