Expansion Block/Orifice Tube: Description and Operation

NOTE: The fixed orifice tube should be replaced whenever a compressor is replaced.

DESCRIPTION
The fixed orifice tube, located in the liquid line near the condenser, has a filter screen located on the inlet 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 (E5VY- 190695) installed if replacement of the orifice tube is necessary.

OPERATION
The fixed orifice tube assembly is the restriction creating the dividing point 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 core and suction accumulator/drier. If the high pressure is higher than normal and the suction pressure drops rapidly creating a faster than normal clutch cycle rate, the orifice tube may be restricted and should be replaced. This condition is usually indicated by the compressor having a short ON time and a long OFF time.