Expansion Valve (Orifice Tube)

Most cars use a thermostatic expansion valve at the evaporator; some use a fixed orifice tube in the line. Some electric cars use electronic expansion valves controlled by the thermal management system. It is the dividing point between the high-pressure and low-pressure sides of the system.

The valve opens more or less depending on the temperature at the evaporator outlet, so the evaporator is fully used without flooding.

A stuck valve can cause poor cooling, frosting or abnormal pressures. Diagnosis is done by reading both system pressures with gauges.