What to Do If Your AC Is Blowing Warm Air

Picture this: It's the middle of June in Tallahassee. The sun is blazing, and the humidity is so thick you can almost see it. You open your door expecting the sweet relief of cool air washing over you, but it doesn't. You place your palm near a vent and realize your AC is blowing warm air through the house or office!

Nothing ruins a summer afternoon faster than coming in from the heat to a warm, stuffy home or business. Your AC switches on, you know it's running, but the air isn't getting any cooler. Before you reach for your phone to call in an emergency service, take a deep breath. 

Not all warm air issues require a service call. Many common causes are easy to diagnose, and you can fix them yourself with no experience or special tools. The trick is knowing what to look for and which issues you need to call in our experts to fix. We put together a checklist of easy fixes that you can check yourself before calling for help. It might just save you time, money, and an afternoon stuck sitting in a warm, sticky house. 

Step 1: Check Your Thermostat Settings

This might seem like a no-brainer, but you would be surprised by how often the thermostat gets bumped or switched to the ‘fan-only’ mode. This is the easiest thing to check, and the quickest fix for an AC blowing warm air. 

Make sure your thermostat is set to 'cool' and the temperature is set to at least a few degrees below the current room temperature. Don't turn it down too fast, or your system could run into other issues. Lower the temperature gradually, a few degrees at a time. 

A programmable thermostat helps prevent this type of issue. However, if you already have yours programmed, make sure it hasn't shifted on its own or been reset accidentally. 

Step 2: Inspect or Replace Your Air Filter

The single most common cause of warm air issues is a clogged filter. A clogged or dirty air filter causes the evaporator coil to freeze up by restricting airflow. Once the coil freezes, air can't pass through, and your AC won't be able to cool your home. 

If your AC is blowing warm, check the filter. The U.S. Department of Energy recommends changing your filter every one to two months during the cooling season. If you can't remember when you last changed it, or it's visibly dirty, swap it for a fresh one. Then turn off the system and wait a few hours for any built-up ice on the coil to melt. Then turn it back on and gradually lower the temperature to a comfortable range. 

While we are on the topic of filters, there are some cases where you can't make the swap yourself. Many homes with newer systems have filter housings that require a more nuanced approach. If you're unsure what type of filter your system uses, it's worth calling a professional to make sure it's done properly.  

Step 3: Clear Debris From the Outdoor Unit

Your system's condenser sits outside where it's exposed to pollen, grass clippings, leaves, dirt, and other debris. If the coils are dirty or the fan is obstructed, the system won't release heat properly. Check to make sure nothing is growing on the unit that could block the fan. Overgrown bushes are a common obstruction. 

If you see an issue, turn off the power to the unit. Trim back any vegetation to at least two feet from the sides. Hose down the coils to remove grime and dirt, and then turn it back on. This is surprisingly common and easy to fix without calling in for reinforcements. 

Step 4: Check for Ice on the Coils or Lines

If your AC is blowing warm air, there could be ice on your coils or lines. If you know where to look, this one is easy to spot. Locate the copper refrigerant line that runs from your indoor handler to the outdoor condenser. It's often covered with black foam insulation. If the foam feels hard or you see frost forming on the line or the outdoor unit's service valves, you have ice buildup. 

This is typically the result of two things. One is restricted airflow, usually from dirty filters or blocked vents. That's an easy fix. The second is a refrigerant leak. That's one you'll want to call a professional for. 

If the issue is ice, switch your thermostat to 'fan only.' This keeps air moving across the coil, which melts the ice faster. Depending on how thick the ice is, it may take two to six hours to fully melt. Once the line or coils thaw, turn the cooling back on. If it works, you're back in business. However, if it happens again within a day or two, you have a refrigerant leak and should call in a professional. 

Step 5: Verify the Outdoor Unit Is Running

Finally, if these steps don't do the trick, and your AC is still blowing warm air, your condenser unit may be the issue. Walk outside and listen for the fan spinning and the hum of the compressor kicking on. If the unit is silent, head inside to check the breaker. If the breaker tripped, flip the switch all the way to off, then back on. Wait a few minutes, then go see if the unit starts back up. 

If the breaker holds, but the unit still doesn't run, and you hear a clicking sound, you may have a bad contactor. That's a task for the experts. If the fan is spinning but the compressor isn't running, it could be a failed capacitor, which a trained technician can easily fix. 

It's important to note that a capacitor can store some electrical charge, even when the power is off. This is absolutely a job for a professional. Unless you have the right training and tools, don't attempt to replace the capacitor yourself.

Still Blowing Warm Air? Give Parker Services a Call!

If you've checked all five of these and your AC is still blowing warm air, it's time to call in the professionals. There are many issues that could be at play, requiring a trained technician to diagnose and fix. At Parker Services, we'll get your system sorted out and back to cooling your home quickly, because no one should have to sweat through a Tallahassee summer. Call us today to schedule an appointment for prompt, honest service!