Orifice Tube

It does the same job as an expansion valve but cannot adjust its flow, so the system controls cooling by cycling the compressor or varying its output. It is common on many American and some older European vehicles. These systems use an accumulator after the evaporator to protect the compressor from liquid refrigerant.

High-pressure liquid passes through a narrow tube with a mesh filter, the pressure drops and the refrigerant evaporates in the evaporator.

Debris from a failing compressor often collects on the orifice tube screen, so inspecting it helps diagnose the cause of a failure. A blocked orifice tube results in poor cooling and abnormal pressures.