Orifice Tube

WARNING: This page is about a different car, the 2002 Pontiac Sunfire and 2002 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.

The orifice tube is located in the liquid line at the condenser outlet. The orifice tube is the dividing point for the high and low pressure sides of the A/C system. As refrigerant passes through the orifice tube, refrigerant pressure is lowered, causing refrigerant to vaporize. The orifice tube also measures the amount of liquid refrigerant that can flow into the evaporator. The orifice tube controls liquid refrigerant flow into evaporator. The orifice tube has filter screens on both inlet and outlet sides. The tube has no moving parts and is not adjustable. Replace orifice tube if plugged or defective.

When engine is turned off with A/C system on, refrigerant in system will flow from high-pressure side to low-pressure side across orifice tube to stabilize system. During this stabilization period, a faint hissing sound will normally be heard for 30-60 seconds.