What is an expansion valve?

An integral part of a car’s air conditioning unit is the refrigerant in the vehicle’s evaporator. The expansion valve (sometimes known as an orifice tube) controls the amount and pressure of the refrigerant that enters the evaporator.
The expansion valve is also where the refrigerant is converted from liquid to gas.
Without a properly working expansion valve, the car’s air conditioning will begin to malfunction. Too much refrigerant will cause the A/C unit to frost, which will prevent the flow of cold air. Too little refrigerant will prevent the air from cooling, leading to a hot cabin.

When do I need to replace my expansion valve?

The expansion valve may be blocked or stuck open. When it is blocked, there won’t be enough refrigerant in the evaporator. If it’s stuck open, there will be too much.
Here are the two main signs it’s time to replace your expansion valve:
  • The air coming from your A/C is not cool
  • The air conditioner isn’t blowing cold air despite the valve being frosty
While not an integral part of the car or a safety feature, components of your A/C unit should be inspected and repaired as soon as your schedule allows.
Your HVAC system is essential to defrosting your windshield in winter, so a malfunctioning unit can impair your visibility on the road. Plus, driving in extreme cold can affect your ability to operate a vehicle.

How to replace an expansion valve

Here’s how a mechanic will replace your expansion valve:
  • Remove the entire refrigerant unit from the A/C system
  • Remove the broken valve
  • Install a new expansion valve in its place
  • Reinstall the refrigerant system
  • Test the operation of the A/C system
Since refrigerant is a regulated substance (not to mention toxic), you shouldn’t try and do these repairs yourself! Take your car to a professional for your expansion valve replacement.