When your central AC gives out in the summer, your house can quickly feel like an oven. Whether your air conditioner is producing weak airflow, not blowing at all, or blowing warm air, you’re likely frustrated and searching for answers.

We’ve helped countless homeowners solve these issues, and we’re here to help you get that cool air flowing again. In this post, we’ll explore why your central AC unit is not cooling and help you figure out if it’s a simple DIY fix or if you need to repair or replace your AC system.

Why Is My Central AC Not Blowing Cold Air?

If your central air conditioner is running but not blowing air, there could be several reasons. Your air conditioner removes heat energy from your home and releases it outside through a precise process with dozens of moving parts. If any part of this process malfunctions, you can be left without air coming through your vents. Here are the most common reasons your central AC unit is not cooling:

1. Dirty or Clogged Air Filter

This is the most common issue, and thankfully, the easiest to fix! Your system’s air filter traps dust, dirt, and other debris to keep your indoor air clean and your air conditioner running smoothly. A dirty filter or clogged filter can block airflow and even lead to other problems with the coils and blower motor.

Fix: Check your air filter monthly and replace it every 3-6 months, depending on the filter you have. A clean filter ensures your central air is producing cool air efficiently. If it’s been a while, simply replace it now! It’s a quick, affordable fix that might solve the problem. Check out our page here to learn more about replacing furnace filters.

2. Frozen Evaporator Coil

A frozen evaporator coil (indoor coil) is a common issue when airflow is restricted. When the evaporator coil gets too cold, ice buildup forms, blocking the cooling process. While this could be the result of a clogged air filter or dirty coil, we usually find that this is the result of a Freon leak. We discuss that below.

Fix: Turn off your AC system and let the evaporator coil thaw for a few hours. Replace the air filter and check the coil (shown below) for debris or loose obstructions. If the issue persists, an HVAC professional can clean the coil or diagnose issues like low refrigerant levels.

3. Low Refrigerant Levels

Refrigerant, aka Freon, is essential for absorbing heat from your home and releasing it outside. A refrigerant leak or even just low refrigerant levels can prevent your AC unit from blowing cold air. A common myth is that air conditioners use up Freon, but the reality is that low refrigerant nearly always points to a leak. These leaks are most commonly in the evaporator coil, where the copper tubing is made paper-thin for efficiency. You can learn more about Freon leaks, here.

Fix: Fixing a refrigerant issue always requires a professional HVAC technician. They can recharge your system with just the right amount of refrigerant and, if possible, locate and repair a leak. Handling refrigerant without certification is against the law and presents a major risk, so leave it to the experts.

4. Electrical or Mechanical Failures

A faulty blower motor, capacitors, or other electrical components can prevent air from blowing through your vents. For example, a failed blower motor might stop airflow, while a bad capacitor could disable the compressor or fan.

Fix: Electrical issues are complex and need an HVAC professional for further diagnosis. They can test and replace faulty parts to restore your AC system’s performance.

5. Ductwork Issues

Leaky or blocked ductwork can prevent cool air from reaching your house. If your air conditioner is running but not blowing air through the vents, obstructions or leaks in the ducts might be the culprit, reducing airflow to certain rooms or the entire home.

Fix: Inspect visible ductwork for obvious blockages. Call an HVAC technician to diagnose and repair any duct damage, leaks, or other issues.

Why Is My Central AC Blowing Warm Air?

We’ve covered what might be going on when you have no airflow. But what if your AC unit is blowing warm air? If you feel hot air actively coming through your vents, it may very well be one of the causes we’ve already mentioned above. But here are some specific reasons we see this issue happen:

1. Thermostat Issues

If you have a curious kid, this may be the culprit! It might sound simple, but it’s very common to see thermostats on the wrong setting, such as “heat” or “fan only” instead of “cool”. If your thermostat is set incorrectly or malfunctioning, it might not signal the AC unit to cool properly. For example, a miscalibrated thermostat set on “auto” might incorrectly read the current temperature in your home and tell your system to run heating mode.

Fix: Check your thermostat settings thoroughly to make sure it’s on “cool” and the current temperature is lower than your home’s temperature. Replace batteries in battery-powered models. If this doesn’t work, call an HVAC tech to check for wiring issues, recalibrate the thermostat, or replace it.

2. Problems with the Outdoor Unit

The outdoor unit, or condenser unit, releases heat from your home. Some common outdoor unit parts that can lead to warm air are faulty contactors, blown fuses, or a bad compressor. Since the condenser coil does most of the work to cool your home and has big, expensive parts, many of the problems happen there. We’ll talk about another common issue with them below.

Fix: Some smaller parts can cost a couple hundred dollars while more serious issues like needing a new compressor can be highly expensive. You can see a breakdown of the costs for different central air conditioner repair prices here.

3. Dirty Condenser Coils

Clogged coils in the condenser unit can prevent your system from releasing heat, causing the AC to blow warm air. They can fill up with things like leaves, dirt, grass clippings, pollen, and cottonwood, leading to reduced efficiency and warm air coming out of your vents.

Fix: You can start by clearing debris within 2 feet of your outside unit to avoid any air blockages. With some AC brands, the outdoor coil is easily accessible and can be rinsed with a garden hose. Others need disassembly and chemicals for proper cleaning. For more info on professional air conditioning maintenance, check out this blog.

4. Heat Pump Malfunction

Heat pumps handle both the cooling and heating side of things for your home. But when the heat pump’s reversing valve or other parts are damaged, the heat pump system might get stuck in heating mode, sending warm air through the vents. This could be a simple thermostat wiring problem where the signal from the stat is not getting to the reversing valve.

Fix: For any issues with your heat pump’s reversing valve or malfunctions with the mode switch, you’ll need to contact an HVAC pro.

Do I Need a New Air Conditioner?

If your older central AC is struggling to produce cold air, you might be wondering whether it’s time to repair or replace it. A common question we hear at Watkins Heating & Cooling is, “How long do central AC units last?” On average, a well-maintained central AC unit lasts 15–20 years. However, frequent issues, poor maintenance, or extreme weather can shorten its lifespan.

If your AC unit is over 15 years old and it’s not cooling because of problems like a failing compressor, repairs may not be a smart investment. A new unit could take your home to a new level of comfort and save you money in the long run with fewer breakdowns and better energy efficiency.

To estimate how much a new air conditioner will cost you upfront, check out our AC Cost Calculator here.

When to Call a Professional HVAC Technician

Some issues, like a dirty air filter or incorrect thermostat settings, are easy DIY fixes. However, complex problems like refrigerant leaks, frozen evaporator coils, compressor failures, or ductwork issues require a professional HVAC technician.

It’s also vital to schedule annual maintenance on your cooling system. Regular maintenance can extend your AC system’s life, because HVAC technicians can catch issues like low refrigerant levels or dirty coils before they become an uncomfortable emergency.

Don’t let a warm house spoil your summer. Reach out to our team at Watkins Heating & Cooling below for fast, reliable service. We’re here to keep your central air working properly.

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