Expansion Block/Orifice Tube: Description and Operation

A/C Expansion (Orifice) Tube:

The plastic expansion (orifice) tube, with its mesh screen and orifice is located in the forward end of the evaporator tube - rear. The expansion (orifice) tube provides a restriction to the high pressure liquid refrigerant in the liquid line, metering the flow of refrigerant to the evaporator as a low pressure liquid.
The expansion tube orifice is protected from contamination by filter screens on both the inlet and outlet sides.