Expansion Block/Orifice Tube: Description and Operation

The fixed orifice tube assembly is the restriction between the high and low-pressure liquid refrigerant and meters the flow of liquid refrigerant into the evaporator core. Evaporator temperature is controlled by sensing the pressure within the evaporator with a pressure-operated electric switch. The pressure switch controls compressor operation as necessary to maintain the evaporator pressure within specified limits.

Orifice Tube Location:

The fixed orifice tube is located in the liquid line near the condenser and has filter screens located on the inlet and outlet ends of the tube body. The filter screens act as a strainer for the liquid refrigerant flowing through the fixed orifice opening. 0-rings on the tube body prevent the high-pressure liquid refrigerant from bypassing the orifice. Adjustment or service cannot be made to the fixed orifice tube assembly which cannot be removed from the liquid line. The liquid line must be replaced, or an Orifice Tube Replacement Kit Part E5VY- 190695-A or equivalent installed if replacement of the orifice tube is necessary.

The fixed orifice tube should be replaced whenever a compressor is replaced. If high-pressure reads extremely high and low-pressure (suction) is almost a vacuum, the fixed orifice is plugged and must be replaced.