The procedure to replace an AC expansion valve replacement will vary depending on your specific vehicle year, make, and model. A technician will first need to evacuate the AC system using a special machine to capture the refrigerant. (It is illegal to vent AC refrigerants into the atmosphere, and only technicians specially certified may service air conditioning systems). Once the system is empty, a technician will generally take the following steps to replace an expansion valve:

• Remove any components that block access to the expansion valve
• Disconnect the 2-4 refrigerant lines connected to the valve housing
• Remove the valve
• Install the new valve with fresh o-rings
• Connect all refrigerant lines
• Using the AC machine, evacuate the system of all air and moisture
• Allow the system to remain under vacuum for up to 30 minutes
• Charge the system with an amount of refrigerant specific to your vehicle
• Start your engine and test the system to verify the repair
• Vehicles where the expansion valve is located inside the passenger compartment will also require that the technician remove lower sections of the dashboard for access and might require removal of the heat-exchange box where the evaporator is mounted. Some vehicle manufacturers may require that the AC receiver/drier be replaced whenever the AC system is opened and exposed to the atmosphere.