What Does An AC Expansion Valve Do? | HVAC Pros Explain (2025)

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Your air conditioner must always work correctly to keep you cool in the summer. AC units have many complex parts that work together to deliver cool, refreshing air. You may be left without that much-needed cool air when one or more parts malfunction.

The AC expansion valve is a critical component in your unit’s function. If your AC unit stops working, there’s a chance it’s due to an issue with this component.

This blog investigates an AC expansion valve and its role in your unit’s operation, common issues you may face, and some DIY troubleshooting tips.

Importance of an AC Expansion Valve: Explained

Expansion valves, or “ex-valves,” are small pressure valves in an AC unit that control refrigerant levels. When hot air enters the AC unit, the refrigerant absorbs it, increasing its pressure. By regulating the refrigerant flow, the expansion valve facilitates the conversion of high-pressure liquid refrigerant to low-pressure liquid, promoting efficient heat transfer. Without this crucial step, the refrigerant will stay in a high-pressure state, which is dangerous. When its pressure levels are lowered, the refrigerant can safely and effectively move through the evaporator coils and push cool air into your home.

Common Expansion Valve Issues

As with any appliance in your home, expansion valves might face issues throughout your AC unit’s lifespan. Things like age, wear and tear, harmful refrigerant, and temperature fluctuations can lead to problems with the expansion valve. Some of the most common issues include:

• Weak or warm airflow: If your unit isn’t producing enough airflow or pushing out warm air, the expansion valve likely fails and cannot correctly regulate the refrigerant flow.
• Ice on the evaporator coils: On the other hand, a faulty expansion valve can make the refrigerant too cold, resulting in frozen-over evaporator coils. This issue may restrict airflow and cooling efficiency.
• Dirt/debris buildup: Dirt and debris can clog the tiny hole on the expansion valve, preventing the refrigerant from entering the evaporator coils and releasing cool air into your home.
• Short-cycling: Is your AC unit frequently turning on and off? If so, your unit’s expansion valve might be malfunctioning and causing the AC compressor to cycle on and off.

Troubleshooting Tips & DIY Fixes for Homeowners

When your unit is on the fritz, it’s good to know what troubleshooting steps you can take to determine the root of the problem and develop a solution. Checking for refrigerant leaks is a good first step. If your unit leaks, turn off your system and carefully remove its refrigerant. You may also need to recharge or refill refrigerant levels.

Ensure all components of your AC unit are tightened and in place. If any are loose, reassemble and tighten as needed. Keep an eye on your unit’s cool air production. Clean all parts to ensure no dirt, dust, or debris buildup. If all else fails, hire a professional for an expert inspection and repair.

Schedule AC Services With Home Comfort Today

Home Comfort has delivered reputable AC services to our Northwest Chicagoland community since 1998. As a proud American Standard Customer Care Dealer, we are confident that we can achieve 100% customer satisfaction. Our background-checked technicians receive thorough training and are equipped with the necessary tools to complete each job. We offer upfront pricing, financing options, and military, veteran & senior discounts for your benefit!

Ready to set up an appointment? Schedule AC services with Home Comfort today.