A/C Orifice Tube
A small metering tube with a fixed expansion hole that controls the flow of liquid refrigerant into the evaporator.
The A/C orifice tube is a small expansion device used in many automotive air conditioning systems. It is typically located inside the inlet pipe of the A/C evaporator core, serving as the dividing line between the high-pressure and low-pressure sides of the system.
The orifice tube contains a small, fixed-diameter brass tube and a mesh filter screen. High-pressure liquid refrigerant from the condenser is forced through the tiny hole, which causes it to expand and atomize into a low-pressure liquid spray. This rapid expansion lowers the refrigerant temperature, allowing it to absorb heat from the cabin.
Because the orifice tube has a fixed opening, it cannot adjust refrigerant flow. The system regulates cooling by cycling the compressor clutch on and off based on pressure switch readings. The mesh filter inside the tube is designed to trap any debris floating in the refrigerant.
If the A/C compressor suffers an internal failure (known as 'black death'), metal debris will quickly clog the orifice tube filter, blocking refrigerant flow and stopping the A/C from cooling. The orifice tube must be replaced whenever a compressor is replaced.