Expansion Block/Orifice Tube: Description and Operation

Air Conditioning Evaporator Tube Orifice

The plastic tube, with its mesh screen and orifice, is located just forward of the evaporator fitting between the condenser outlet and evaporator inlet. It provides a restriction to the high-pressure liquid refrigerant in the liquid line, metering the flow of refrigerant to the evaporator as a vapor. The evaporator tube orifice is protected from contamination by filter screens on both inlet and outlet sides.

When system diagnostics indicate a restricted evaporator tube orifice, it may not be necessary to replace the tube. Metal chips, flakes or slivers found on the screen may be removed with compressed air and the evaporator tube orifice may be reused if:

^ The plastic frame is not broken.
^ The brass expansion tube is not damaged or plugged.
^ The screen material is not torn.
^ The screen is not plugged with fine gritty material.