Evacuating the System

Evacuating the System
This process, the removal of unwanted air and moisture, is critical to the correct operation of the air conditioning system. The specific procedures will vary depending on the individual characteristics of your chosen recovery/recycle/recharge equipment and must be carried out exactly in accordance with the manufacturers instructions. However, it is recommended that the initially only the HIGH side valve be opened at the start of the procedure. After a short time a small depression should be seen on the LOW side, at which point the LOW side valve may be opened and the evacuation process completed. If a vacuum is not registered on the LOW side it may indicate that the expansion valve is jammed closed or that the system is blocked. This simple check may save time and effort when the system is recharged.
Moisture can be highly destructive and may cause internal blockages due to freezing, but more importantly, water suspended in the PAG oil will damage the compressor. Once the system has been opened for repairs, or the refrigerant charge recovered, all traces of moisture MUST be removed before recharging.