Why Is My Central AC Not Blowing Cold Air?
Key takeaways:
• Multiple issues, from a dirty or clogged air filter to a refrigerant leak can result in your AC unit not blowing cold air.
• Only a licensed HVAC technician should repair your system.
• Many American Standard dealers provide 24/7 emergency AC repair.
By Anne Fonda
What did we do before central air conditioning? We’ve grown used to the cool comfort of our home on a sweltering summer day. If you just came home and your AC unit is running but not blowing cold air, you’re looking for answers. Well, you’re in the right place.
Top 6 reasons why your house AC is not blowing cold air
Reasons for an air conditioner running but not blowing cold air run the gamut, and the solution can range from simple fixes to major repairs. A few examples:
1. Thermostat issues
When you ask yourself, “Why is my air conditioner not blowing cold air?” check your thermostat before you call for HVAC repairs. You can do this via the Home App if you have one of our smart thermostats, or at the thermostat itself. Do the following.
- Make sure your thermostat is set to COOL.
- Make sure the fan is set to AUTO, so the system only blows air when the AC unit is running. If the fan is set to ON, it will blow warm, unconditioned air even when the air conditioner isn’t running.
- Make sure the set temperature is lower than the current indoor temperature.
- If your thermostat uses batteries and the thermostat screen is blank, replace the batteries.
If it’s not a simple thermostat issue, check the filter next.
2. Clogged air filter
Another reason it may feel like your AC is not blowing cold air is reduced airflow. A clogged or dirty HVAC air filter can cause low airflow, a frozen evaporator coil, or even cause a system shutdown. Check the air filter, and if it’s dirty, replace it.
Get in the habit of changing the filter every 1-3 months year-round. Read our HVAC air filter replacement guide for some handy tips.
If this doesn’t solve the problem, you probably need to call for AC repair. Here are some other potential causes of a home AC unit not blowing cold air.
3. Clogged condensate line or drain pan
When your air conditioning system is running, it not only cools your home, but it also pulls moisture from the air. This water vapor (condensation) drips into a condensate pan and then into a condensate drain line at the indoor air handler or furnace. Over time, dust, spider webs, cobwebs, mold, or mildew from standing water can cause a blockage in the drain line.
Some indoor units have a drain pan condensate safety switch that shuts down the indoor unit if the water level inside the drain pan begins to rise. Fixing the issue is best left to a trained HVAC technician. But you can ask them what you can do to keep the drain line and drain pan clear in the future.
4. Frozen evaporator coil
A frozen evaporator coil can also be the cause of your AC running but not cooling. The evaporator coil is the indoor coil, located next to your furnace or inside the air handler. Some people call it the furnace coil or the “A” coil because of its shape.
During the refrigeration cycle, cold refrigerant flowing through it absorbs the heat from inside your home and transfers it outside. At the same time, air blows across the cold evaporator coil, cooling it before it enters the ductwork system.
Over time, dirt and debris such as pet hair can collect on the evaporator coil, preventing proper air circulation. This can cause the coil to frost over or freeze, which can result in a refrigerant leak. A dirty filter can also cause a frozen evaporator coil. If you see that your coil is frozen, turn the HVAC system off and contact an HVAC company for help.
5. Dirty condenser coil
The condenser coil is the outdoor coil in your AC unit. It dissipates the heat that the refrigerant absorbed from inside your home before the next step in the refrigeration cycle.
Over time, dirt, grass clippings, pollen, and other debris can get inside the unit. A dirty condenser coil can lead to decreased cooling efficiency, longer cooling cycles, and even system failure.
You can help prevent this by mowing with the mower discharge pointing away from the AC unit, keeping debris off the top of the unit, and keeping plants at least two feet away from the sides of the unit. You can also gently hose down the outdoor coil. For complete coil cleaning, call an HVAC professional.
6. Low refrigerant level
Another reason for your AC blowing warm air instead of cold air is that it’s low on refrigerant. For most air conditioning systems, this is never an issue. However, low refrigerant levels can result from a refrigerant leak or incorrect charging at installation.
Either way, you need an HVAC professional to determine the fix. They will do testing to try and find a leak, fix it if possible, and recharge the unit if it makes sense to do so.
Low refrigerant levels can cause a frozen evaporator coil, just like a frozen evaporator coil can cause a refrigerant leak. If it’s a large leak that can’t be fixed, you may need an expensive replacement part or a new unit.
Weigh the pros and cons of repair or replacement
If you know your HVAC technician by name because you’ve had so many repairs, depending on what this latest repair is all about, they may suggest you start thinking about replacing your aging air conditioner and even your whole HVAC system. There are a lot of reasons for this. As long as they can get your air conditioner working again, there’s no rush.
Learn more in these select blogs to help you make an informed decision.
Prevent problems with regular maintenance
“Regular maintenance is the key to avoiding an unexpected shutdown, but even if you do find your system not working, an American Standard HVAC tech can find the problem quickly and get you back on track.”
- Mark Woodruff, Senior Product Manager, Air Conditioners
By simply changing the filter every 30-90 days, you can prevent a lot of problems. In addition, keep the area around the outdoor unit clear. Finally, schedule professional AC maintenance every spring before the cooling season begins. This allows an HVAC technician to spot small problems before they become big issues.
For example, if they see that the evaporator coil is coated in dirt and pet hair, they can clean it. There may be an extra charge for this, as coil cleaning is not usually included in a routine AC tune-up. But it will still be cheaper than coil replacement.
Get help now
Contact your local American Standard dealer for AC repair to get your home cool again. Many dealers offer 24/7 emergency repair services. And if you’re thinking about replacing your system, you can schedule a free quote.
Anne Fonda, Content Writer
A Content Writer with Trane Technologies, Anne Fonda researches topics and writes for Trane® and associated residential HVAC brands. She works in collaboration with Trane Technologies subject matter experts, offering easy-to-understand, informative content on complex topics. Her goal is to help consumers make informed decisions on the products and services they need.
She has written for HVAC and other service provider websites for over 16 years. Before transitioning to web content writing, Anne had a 14-year stint as an award-winning journalist. She graduated cum laude from the University of Missouri-Columbia School of Journalism.
When she’s not working, Anne enjoys playing word games, reading, gardening, spending time with family, and visiting gardens and museums.
Expert review by Mark Woodruff, Senior Product Manager, Air Conditioners
