A/C Expansion Valves & Orifice Tubes

Expansion valve and orifice tube both separate the low (suction) and high (discharge) sides of the A/C system, regulating the flow of liquid refrigerant through the evaporator. The expansion valve does this by adjusting pressure with moving internal parts and a sensor that reads the temperature of the refrigerant, while the orifice tube is a fixed piece that meters the flow and causes the compressor to adjust pump capacity or completely switch on and off.

If working properly there will be a more consistent A/C temperature in relation to your settings, an improved performance in traffic compared to while in motion, and a reduction of condensation in the A/C evaporator. Most also have a filter screen that catches contaminants. It is best to flush the system after installing the new device whether or not you notice any trapped debris. This will help prevent any future failure of the new part.

Failure to replace an old worn out expansion valve or orifice tube can be detrimental to the proper function of the A/C system. If the calibration is incorrect the evaporator may stop exchanging heat correctly or even freeze up due to excessive condensation. If the problem has yet to become catastrophic you would notice varying performance between when you are cruising and when you are at idle. You may even notice that the temperature is not consistently matching the setting on the gauge that you are trying to achieve.

If you notice that your A/C system is not cooling properly, the pressure readings in the gauges are irregular, or the evaporator is freezing up, it would be best to check the functionality of these devices. Failure to replace the device in time may cause a backup in pressure that will damage your compressor/clutch assembly. Then you will meet a much more expensive project. Instead of getting heated over a simple fix, chill out and replace your expansion device!