Expansion Block/Orifice Tube: Description and Operation

EXPANSION (ORIFICE) TUBE DESCRIPTION





IMPORTANT: Small amounts of debris or metal chips is considered a normal condition.

The plastic expansion (orifice) tube (2) is made of a mesh-screen (1) and orifice (3). The expansion (orifice) tube is located in the evaporator inlet pipe at the liquid line connection. The tube restricts the high pressure liquid refrigerant in the liquid line. Metering the refrigerant flow to the evaporator as a low pressure liquid. The expansion tube and orifice have filter screens which protect from contamination on both the inlet and outlet sides of the tube. The expansion tube is sealed inside the refrigerant pipe by an O-ring. This O-ring is necessary for proper operation of the refrigerant system. When the engine is OFF and the A/C is running, the refrigerant in the system flows from the high pressure side of the tube to the low pressure side until the pressure is equalized. This may be detected as a faint hissing sound for 30-60 seconds and is a normal condition.