Mercedes-Benz S400 Expansion Valve (Orifice Tube) Replacement at your home or office.

What is the Expansion Valve (Orifice Tube) all about?

The air conditioning system in your vehicle depends on the refrigerant that circulates in the A/C system. In particular, the evaporator core inside the passenger compartment requires a specific, metered amount of refrigerant in order to efficiently cool the interior. The expansion valve, also known as an orifice tube in some designs, regulates the pressure of refrigerant that enters the evaporator. The tube is also where liquid refrigerant under pressure converts to a gaseous form. The gaseous refrigerant absorbs heat from air passing through the evaporator core and carries it to the condenser where the heat is removed.

In a situation where the orifice tube is either blocked or stuck open, the air conditioning will not cool properly. Too much refrigerant will cause frost on the core and prevent air from passing through to cool the air temperature. Too little refrigerant passing through the evaporator means not enough heat is absorbed and the interior is insufficiently cooled. In either situation, you may need to replace the expansion valve/orifice tube.