13. With the main unit mostly secured, it was time to attach the high pressure (blue cap) and low pressure (red cap) fittings to the unit. These 90-degree fittings require O-rings (included) for proper sealing with the Freon. Before installation, be sure to wet the O-rings with the included refrigerant oil. Once the lower pressure line secured, the control valve temp probe (copper coil) is attached to the fitting using some of the enclosed insulating tape. This probe controls the system, and if the temperature of the evaporator gets too low, will cut off Freon flow to the unit.