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A/C Expansion Devices: The Difference between an auto air conditioning Orifice Tube  and an auto air conditioning Expansion Valve

The expansion device is a small but important part of all auto ac compressor kits. The purpose of an Expansion Device for a vehicle’s Air Conditioning System is to control the difference in high pressure and low pressure in the system and ultimately to prevent moisture from freezing on the evaporator. This is important because moisture freezing on your Evaporator can likely lead to A/C Compressor failure or malfunction. The common two types of Expansion Devices used with A/C Systems are Orifice Tubes and Thermostatic Expansion Valves. Both of these act as a control device between the high and low pressure of the system, but are definitely different in execution.

An auto air conditioning Orifice Tube is a commonly used Expansion Device that uses its tube diameter to transfer refrigerant to the evaporator. However, the Orifice Tube, itself, does not actually manipulate the amount of refrigerant entering the Evaporator. Instead, when using an Orifice Tube, refrigerant flow is fixed at all times and the compressor will take the refrigerant flow into its control. The compressor will engage and disengage to control refrigerant flow in the system based on the demand for cool air in the vehicle.

A Thermostatic Expansion Valve is another common Expansion Device which sometimes has a “Block” look rather than a tube appearance. Unlike the Orifice Tube, an auto air conditioning Expansion Valve, itself, actually adjusts the flow of refrigerant to the Evaporator based on the demand for cool air in the vehicle. The Thermostatic Expansion Valve is very accurate in refrigerant control for your system as it uses a metered system to ensure exact refrigerant flow based off of the demand for A/C.