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October 25, 2023

Understanding the Role of an AC Expansion Valve

Do you need help with your cooling or heating system? Complete Comfort Heating, Air & Plumbing can help when you call us today.

Is your air condition making a weird whistling noise or blowing warm air? You might have a problem with your AC expansion valve.

As the top air conditioner repair in Avon, IN, Complete Comfort Heating, Air & Plumbing feels passionate about keeping your HVAC systems working. Keep reading to discover everything you need to know about your air conditioner’s expansion valve.

What Is an AC Expansion Valve?

To understand the role of the expansion valve, you need to know what role refrigerant plays in your air conditioning system. Refrigerant transitions between a liquid and gaseous state, and its primary role is absorbing heat and carrying it outside to release it. When it’s cooled, it passes through the indoor evaporator coil to absorb heat, and then it moves to the outdoor condenser coil, where it releases it, leaving the cool air to blow throughout your home.

However, when the refrigerant leaves the condenser in liquid form, it’s too hot and pressurized for effective evaporation. This is where the expansion valve plays a crucial role.

The Valve's Purpose

Also known as the thermal expansion valve, this component serves two main purposes.

  1. Maintaining pressure: Low pressure is essential for cooling efficiency because the refrigerant requires it to return to its gaseous state, which allows it to release the heat. Because refrigerant needs considerable space to expand, the valve allows only a small amount to flow into the evaporator at once.
  2. Keeping the air cool: While the expansion valve isn’t one of the HVAC components that directly affect temperature, it’s an important piece in keeping the air cool. If you’re air conditioner can’t complete the refrigeration cycle, it blows out lukewarm or hot air.

Common AC Expansion Valve Problems

You can tell your AC expansion valve needs attention if you notice one of the following problems.

Blowing Warm Air

While several issues could cause your air conditioner to blow warm air, a faulty expansion valve is one of the most common. The valve might have a leak, or low refrigerant levels might prevent the valve from distributing enough of the substance to the evaporator coil.

If the issue is low refrigerant levels, only a professional should refill it. Refrigerant is a toxic chemical and requires special methods of handling and disposal.

Constant Running

In a fully functioning air conditioner, the expansion valve closes once your home reaches the desired temperature, which allows the compressor to shut off. If the expansion valve fails to regulate the flow of refrigerant, the substance continues to enter the coil, and it won’t turn off as it attempts to evaporate the gaseous onslaught. 

When the air conditioner runs constantly, you’ll see your energy bills skyrocket, and your home will feel too cold. But the greater concern is the toll it takes on your compressor. Without rest, the critical component wears out faster and requires replacement sooner, which usually costs a couple of thousand dollars.

Making Whistling Noises

A whistling noise occurs when the refrigerant flows from the valve with too much force. It indicates the valve isn’t maintaining the correct pressure, which, at the very least, affects its efficiency and increases your energy bills; at worst, it can cause further damage to your air conditioner.

Inconsistent Air Temperatures

While a faulty expansion valve can lead to consistently warm air, at other times, you might feel the temperature fluctuate for no apparent reason. This means, rather than a complete failure, your expansion valve is struggling to consistently regulate the flow of refrigerant. Your temperatures might range from excessively cold to as hot as the air outside.

Frozen Coils

If your expansion valve lets too much refrigerant onto the coil, it might run constantly, or it could just freeze over when it gets too cold. This can happen even during the hottest days in summer and indicates you have a problem with your refrigerant levels or expansion valve.

If you see ice accumulating in your air conditioner, shut it off immediately and call your HVAC technician for emergency repairs.

Replacing Your AC Expansion Valve

The more you use your air conditioner, the faster your expansion valve wears out. However, with moderate use and regular air conditioner maintenance, the valve should last 5 to 10 years.

Always replace your expansion valve quickly. In the hottest days of summer, a broken air conditioner constitutes an emergency. A broken expansion valve can also lead to more expensive repairs, and the cost of a new valve is a fraction of the expense compared to other components.

When you call an HVAC technician to replace your expansion valve, they will typically follow these steps:

  1. The technician will shut off the air conditioner and unplug it or turn off its power at the circuit breaker.
  2. They’ll remove the casing on the indoor portion of your air conditioner and locate the expansion valve.
  3. The technician will lock the refrigerant lines to avoid any leaks.
  4. Next, they remove the valve and replace it with a new one.
  5. Finally, they close the air conditioner, restore power, and test the new valve.

While you can find guides that tell you how to install a new valve yourself, to avoid further damage or health complications from the refrigerant, always hire a certified professional for the job.

Let Complete Comfort Heating, Air & Plumbing Fix Your HVAC System

Do you suspect you have a faulty AC expansion valve? With over 20 years of experience, the team at Complete Comfort Heating, Air & Plumbing provides exceptional service at a competitive price. With over 75% of our business coming from referrals, we’re confident you’ll love our service.

From helping you find the best AC unit placement to fixing even the most complicated HVAC components, we do everything we can to keep your home safe and comfortable year-round. Call (317) 804-4449 to schedule an appointment today.