Expansion Block/Orifice Tube: Description and Operation

NOTE: The A/C evaporator core orifice should be replaced whenever an A/C compressor is replaced.

The A/C evaporator core orifice has the following characteristics:
^ is color coded orange.
^ has a diameter of 1.46 mm (0.058 inch).
^ is located in the condenser to evaporator tube.
^ has filter screens located on the inlet and outlet ends of the tube body.

The A/C evaporator core orifice assembly is the restriction in the refrigerant circuit that creates the pressure drop necessary for cooling by metering the flow of liquid refrigerant into the A/C evaporator core, reducing the pressure.

Operation is as follows:
^ The temperature of the A/C evaporator core is controlled by sensing the pressure within the A/C evaporator core with the A/C cycling switch.
^ The A/C cycling switch controls compressor operation as necessary to maintain the pressure in the A/C evaporator core within specified limits.
^ The inlet filter screen acts as a strainer for the liquid refrigerant flowing through the A/C evaporator core orifice.
^ O-ring seals on the A/C evaporator core orifice prevent the high-pressure liquid refrigerant from bypassing the A/C evaporator core orifice.
^ Adjustment or service cannot be made to the A/C evaporator core orifice assembly. It must be replaced as a unit.
^ The condenser to evaporator tube must be replaced, or an Orifice Tube Replacement Kit or equivalent installed, if replacement of the A/C evaporator core orifice is necessary.