AC Unit Running, But No Air Is Coming Through Vents (Why?!)
homedude is reader-supported. When you buy through links on our site, We may earn an affiliate commission. Learn more
Air conditioning is the epitome of comfort, and we typically take it for granted, not even paying much attention to it. But, when your AC is running, but no air comes through the vents, you can bet you take notice. And if it’s a particularly sweltering day, you want to fix it as soon as possible.
If your AC is running, but there’s no air coming through the vents, something could be blocking a duct. You could also have a dirty filter, incorrect thermostat settings, frozen coils, or your unit’s struggling if it’s a scorching hot day. You can do some basic troubleshooting first, but if the problem persists, call an HVAC professional.
Certain AC repairs can turn into more significant problems if you attempt them yourself. Sometimes even something that seems like a minor repair could lead to big problems if done incorrectly. Therefore, start with simple possibilities that are DIY-appropriate, then know when to call it quits.
6 Reasons Your AC Is Running, But No Air Is Coming Through The Vents
If you hear your AC running but don’t feel any air coming through the vents, it could be several things.
1. Your AC Isn’t On; It’s Just The Attic Fan
Sometimes, the simplest solution is all it takes. Are you sure your AC is actually running? The noise you’re hearing might just be the unit’s fan working in your attic.
The fan helps pull hot air out of your house, so it doesn’t come back into your home. The typical suggestion is to leave the fan running, but that doesn’t mean your AC is running too.
Check the thermostat. If the fan is on, but you don’t feel air coming through the vents, you need to decide what is going on with your AC. Why isn’t it running and cooling your home as it should?
There could be a faulty part, or maybe you need a new AC. But first, before fearing the worst, continue troubleshooting through the following steps. The reason could be one of the following issues.
2. Someone Changed The Thermostat Settings
If it’s just the fan you’re hearing, and the AC hasn’t actually kicked on, check your thermostat settings. It could be that someone changed the setting without your knowledge or accidentally. For example, perhaps someone switched the mode button to heat by accident or raised the temperature in cool mode.
Either way, if the thermostat is set above the temperature in your home, your AC unit won’t run. So, make sure it’s set to cool and lower the temp to see if that gets the cool air flowing.
3. Your AC Has A Filthy Filter
If all of the thermostat settings look correct, check the filter. When’s the last time you cleaned it? Typically, it’s best to change your air filter monthly.
Some types of filters can go three months. And some heavy-duty specialty models last 6 months, and typically your HVAC professional changes them out during your semi-annual service appointment.
The filter is responsible for keeping dust, debris, pests, and other unwanted items from getting into your unit. It helps prolong the life of your AC and keeps it running efficiently. But, all of the dust and stuff it catches stays on the filter and builds up.
So, if you neglect to change the filter, eventually the filter will get so filthy, it will block the airflow. Not only will it keep air from coming through the vents, but it will also cause your AC to work overtime. This extra effort leads to your AC wearing out faster, not to mention pricier utility bills.
4. It’s An Extremely Hot Day
Check the temperature; is it sweltering outside? When the weather is intensely hot, even an AC in good working condition can struggle to cool things down enough. On extremely hot days, it’s not uncommon for your AC to only get your home’s temperature to a certain limit.
For example, if it’s 100 degrees outside and your thermostat setting is 68, your house might not get below 82 degrees. This is actually normal for unusually hot days in your area. But, technically, your AC is still working, and you should feel some air coming out of the vents.
However, if you keep trying to crank down the AC to cool your home, it will start to work overtime. When this happens, you might notice the air stops flowing, likely because your unit freezes up.
You can literally wear out your AC, and it can experience a burn-out or some type of damage. When it’s crazily hot outside, help your AC out a bit. Resist the urge to crank it down and set it to a more reasonable number like 78 or 80 degrees.
Then supplement its efforts with fans to help keep things comfortable. Also, close shutters or drapes to block out bright, hot sunlight and help keep your home cool.
5. Something’s Blocking A Duct
Although it might not happen often, something could block the central duct of your AC unit. If no air can get through here, it can’t get to any of the other ducts. This blockage means no air coming through any vents.
If you just don’t have air coming out of one vent, it could just be that particular duct blocked. Or the register for the vent is closed.
The duct could have a dead animal inside. Or perhaps a box or heavy item in your attic has fallen on top of a duct. You can inspect the ductwork to see if you notice any visible issues. But if you are unsure, call a professional to inspect your ducts.
6. Frozen Condenser Coil
For various reasons, if air can’t properly move through your AC unit, the condenser coils will freeze up. This iciness happens when the condensation created by the AC as it cools sits on the coils. Typically, the coils rely on the air moving through the system to evaporate some of this moisture.
But when the condensation builds up, it can freeze the coils. You’ll hear the AC kick on, but you won’t feel any air. Turn off the AC (you need to let the ice start melting) and call an HVAC professional.
Tips For Proper AC Maintenance
To keep your AC running in tip-top shape, practice these maintenance tips.
- Change the filter regularly based on the type you’re using. If it is a permanent style filter, you need to make sure to clean it regularly.
- Keep the outside AC unit clear of debris like leaves and weeds. If your dryer vents outside near the unit, this is also a possible source of dust.
- Keep about two feet of space clear around the AC for adequate airflow.
- Don’t place the outside unit below a patio roof or similar cover. This placement causes hot air just to recirculate and push back down on top of the unit.
- Have a professional HVAC specialist service your unit once a year before summer and once a year before winter.
Frequently Asked Questions
What if my AC is on, but it’s only blowing hot air?
Several things can cause your AC only to blow hot air, primarily low refrigerant levels. You could have a freon leak.
There could also be a damaged compressor, clogged valve, or wiring issues. Your best course of action is to turn off the AC and call a professional to inspect the unit.
How much does a typical AC service call for regular maintenance cost?
On average, professional servicing of your AC costs about $100 to $150. This price usually includes inspecting and tightening all of the unit’s parts (outside and inside the house). It also includes cleaning the coils and addressing minor issues.
If you have a specialty filter installed, you might pay about $25 to $50 more. If you need the specialist to recharge your refrigerant, it can add another $100 to $200, depending on how much you need. Some companies will set you up on a contract to come out twice a year and offer a small discount.
What is the average lifespan of an air conditioner?
An AC unit lasts roughly 15 to 20 years at its optimum performance. However, proper care can extend this lifespan. If you get regular maintenance, change the filter routinely, and keep your unit clear of debris, you could add about 5 years to its life.
Conversely, fail to regularly change the filter or call for service, and your unit might only last 12 to 15 years. Also, if your AC experiences any problems, address them promptly. Immediate attention and repair can make all the difference in keeping problems from escalating.