Why Is My AC Only Blowing Warm Air? Can I Fix it Myself?

The reason your air conditioner is only blowing warm air can be anything from a small, easy-to-fix item to a more significant problem.

In this article, we’ll outline four common reasons why this happens. You can fix two yourself, but the others require a professional. And, we’ll give you the heads-up about the one that may require a full replacement.

Meanwhile, if you have any questions about the air conditioning in your home in or near Havertown, PA, call or email us here at John Cipollone.

Dirty HVAC Filter

A dirty, clogged HVAC filter is a common cause for your AC blowing warm air. And, it’s an easy one to fix. If you’re keeping up on your maintenance, you’ll take care of this problem before it happens.

The filter traps dust, dirt, and contaminants as they pass through your system. It prevents that stuff from circulating through the air.

But, eventually, the filter gets clogged. At that point, it doesn’t even let the air through.

When it comes to air conditioning, a lack of airflow can result in warm air coming through the vents. The blockage prevents air from passing over the condenser, which is the part that handles the cooling.

As a result, any air that’s making it through the ductwork is still warm.

How to Fix It

The quick, easy fix here is simply buying a new air filter and swapping it with the old one. Filters are inexpensive and easy to find at any hardware store.

We recommend changing the filter monthly. If you have pets, allergies, or respiratory problems, every few weeks is even better.

And, if you’re concerned about your indoor air quality, you can choose a stronger filter that helps make your home more comfortable and healthy.

Stronger filters block smaller and smaller particles. The average one-inch-thick models do a good job blocking dust particles and similar particles. But, if you suffer from allergies or get sick easily, look into a filter with a higher MERV rating.

Those models will block pollen and other allergens, along with bacteria, mold spores, and even some viruses.

“Regular”  filters are usually up to 5 MERV. For your home, a screen up to 13 MERV makes a big difference. Anything higher than that can restrict airflow because residential furnaces usually aren’t strong enough to push air through a screen that restrictive.

Incorrect Thermostat Settings

Next, check the settings on your thermostat. For air conditioning, set it to “Cool,” and the fan on “Auto.” If these are different, you may get warm air when you want it cold.

Of course, during the winter, you’ll have it in heating mode. And, in some cases, the fan may be set to “On” or “Circulate.”

Bottom line: if you’re set to heat, or just running the fan, or asking the thermostat to make your house warmer than it already is, the system will blow warm air when you want things cooler.

How to Fix It

Another simple fix: Adjust the settings!

First, set the fan to “Auto.” If you set it to “On,” then it’s circulating the air in your house, not providing cooling.

This setting is useful during shoulder seasons when it’s neither too hot nor too cold.

In the early spring, for instance, you probably still have your windows closed without running the heat or AC. As a result, any dust or other contaminant in your house build up. With no open windows, they have no place to go.

Letting your HVAC system circulate the air helps with that problem. As the air passes through the filter, it gets rid of those pollutants.

But, once you want air conditioning, set it to “Auto.”

And, consider setting your AC to 78 degrees. It seems high, but according to the US Department of Energy, it’s the ideal setting to stay cool while keeping your bills low.

Refrigerant Leaks

Your air conditioner requires refrigerant fluid to keep you cool. That fluid runs in a closed loop through the system. The heat in your home turns it into a gas, and then it turns back into a liquid as the system cools the air, releasing that thermal energy.

Ideally, you should never run out of refrigerant: The same batch keeps traveling through the system. If you have a leak, however, you’ll notice a problem as the level gets low.

What’s when you start getting warmth instead of cooling. The air in your home travels through the system as it should. But, without enough coolant, there’s nothing to remove the heat. Then, the warm air recirculates inside.

How to Fix It

Unfortunately, this problem requires a professional. First, they need to find the spot —- or spots — from where the coolant is leaking.

Then, a tech needs to repair the break and recharge the system. It’s a straight-ahead process — unless your system is more than ten years old.

R22 Refrigerant

Before 2010, ACs used R22 freon for coolant. But, since it’s bad for the environment, the EPA began phasing it out.

Starting in 2010, manufacturers used a different coolant for new units. Manufacturers began producing less and less R22.

At the start of 2020, no manufacturers produced any more R22. So, supplies are limited and getting more and more scarce.

We covered this in more detail here. But, the bottom line is that a coolant leak on an older system means you’ll most likely have to replace your air conditioner.

If you catch it early enough, we may be able to provide a small recharge if you still have a lot of coolant.

But, if it’s to the point where the system isn’t working, odds are the cost of the recharge makes the repair not worth the money.

Broken Return Duct

When you think of ductwork and vents, you usually imagine air blowing out of them. But, just as important are the return ducts. They draw in air from the rooms in your house.

For air conditioning, your system cools the air that your return ducts draw in. Then, the treated air blows back out of your vents.

If your return duct is leaky, broken, or obstructed, this won’t work correctly.

Of course, any duct problems can lead to HVAC issues. But usually, if there’s a leak or broken duct elsewhere, you’ll just have low airflow. That’s because the problem occurs after the point in the process where your air gets cooled.

How to Fix It

Unfortunately, this is another job for a professional. Even if you can spot the break visually, the last thing you want to do is tinker with it. There’s a good chance you’ll make things worse.

The best you can do is troubleshoot some of the other items here, particularly your filter and thermostat. If you fix one of those and the problem goes away, you saved yourself a service visit.

However, if you’ve looked over the more straightforward, DIY fixes and your AC still blows warm air, call or email us here at John Cipollone.

With nearly a half-century of experience in Havertown, the Main Line, and across Delaware and Montgomery counties, we’ll have your home cool and comfortable again as quickly as possible.