It’s incredibly frustrating when you can’t get cool on a hot day, even though your air conditioning sounds like it’s working (it’s blowing). Is it you, or is it sweltering in here? You check the thermostat, and the temperature is soaring well above the set temp. When you place your hand over one of the AC registers, you find your AC blowing warm air. What’s going on? Is your AC blowing warm air because of a simple issue you can fix yourself, or is your AC, not 4-ton multi zone split AC?
Read on to learn about the most common causes of an AC blowing warm air and which ones you may be able to tackle yourself.
9 crucial causes of AC blowing warm air
Your AC is blowing warm air because while the fan is operating, something is shutting down the cooling mechanism. Causes include simple things like thermostat settings and poor airflow, but they also could be issues that can spell big trouble, like electrical problems and refrigerant leaks. We’ll start with the easy issues you can fix and let you know when you need the skills of a professional to diagnose and repair a more significant problem.
1-Thermostat issue
Whether you’re worried about your home or workplace AC blowing warm air, the first thing to check should be the thermostat. It’s a fact: they get tampered with by kids accidentally hitting it with a flying object or a co-worker turning it off because of being too cold.
Ensure the thermostat is set to COOL and the fan is set to AUTO. And, of course, the set temperature is lower than the air temperature.
2- A clogged filter
Reduced airflow is one of the most common problems that can impede the cooling operation of your air conditioner. Strange though it may seem, your air conditioner needs warm air flowing over the coils to function correctly. Your air conditioner’s filter is designed to remove dust and contaminants from the air flowing through the equipment. However, an air filter clogged with dust and debris can completely block air from entering the system. When that happens, the coils can’t remove heat. So, your system’s fan blows heat back into your space.
If you haven’t had your system maintained in a while and your AC is blowing warm air, the next step is to check your air filter and change it if needed.
3- Return vents closed or blocked
Here’s another airflow issue that can result in your AC blowing warm air. Is it possible that vent grilles were closed over the winter and never re-opened? Or (common in offices!) do you have furniture or other obstructions blocking them?
Take a walk around your space and ensure all registers and returns are open, allowing air to flow freely.
4- Disconnect or leaky ducts
It’s also possible that you have airflow problems that you can’t see… in your ducts. If a duct has holes, cracks, or is entirely disconnected, return air may not be making it back to the unit. Or cooled supply air may be wasted in your walls, attic, or crawl space, and the AC blows warm air.
If your ducts are accessible, you might want to take a look. It’s not uncommon for damage to occur during construction projects or from birds or rodents getting into them. On second thought… this might be an area where you’re better off getting professionals to inspect the condition of your ductwork.
5- Loss or power to the outdoor unit
Many air conditioning systems have indoor evaporator/air handler and outdoor condensing units. (In areas like NYC, where there’s not much access to outdoor space, your “outdoor” condensing unit may be in a mechanical room). The fan will still blow air into your space if the air handler works fine. But without the condenser unit working correctly, there will be no cooling; hence, your AC is blowing warm air.
That scenario can happen when your condenser unit loses power, often due to a blown a fuse or tripped circuit breaker. If you discover that your outdoor AC unit keeps tripping the circuit breaker, read this to find out what to do next:
Note
Never try to diagnose electrical issues yourself unless you are a trained electrician or HVAC expert. Live voltage is not something you want to experiment with! There is one thing you can check, however: your emergency shutoff switch. It may have been accidentally shut off, cutting the power to your condenser unit and leading to your AC blowing warm air.
6- Dirty condenser coils
One of the essential functions of your condenser unit is releasing heat to the outside of your building. The condenser coil is responsible for that job. Because it’s exposed to the elements, it can get caked with dirt and grime, not to mention leaves and trash. Eventually, that impedes the operation of the coils, and your system can’t cool effectively, so the AC is blowing warm air.
7- Dirty evaporator coils
In the indoor air handler unit, evaporator coils are crucial in how your AC system cools the air. It’s where the hot air is absorbed and cooled by refrigeration. These coils, however, can become dirty or clogged, restricting their ability to cool the air properly. If this is the case, your AC unit won’t be able to cool your home efficiently, and warm air may blow instead.
While it may be best left to a professional technician, you can clean the coils yourself by following these steps:
- Turn the AC system off, preferably at the panel and the breaker.
- Locate the coils. They will be housed in the air handler near the blower fan. You may need to consult the manual or other resources if you have trouble finding them.
- Fill a spray bottle with warm water and regular household cleaning detergent.
- Spray the solution and let it sit for up to 10 minutes.
- Gently wipe away the debris from the coils with a soft cloth.
8- Refrigerant leak
Refrigerant is the substance that flows through your air conditioning system and (to make a long story short) makes the cooling happen. It’s a closed loop, so you should not need to add refrigerant unless there’s a leak in your refrigerant line or the coils. When that happens, your system loses refrigerant charge and cooling power. Depending on the size of the leak, the cooling loss can happen slowly or all at once, but eventually, your AC is blowing warm air.
9- Multifunction generator
Your air conditioning unit depends on refrigerant to be cycled through the unit in order to blow cold air when it is turned on. If the compressor in your unit is malfunctioning, the refrigerant is unable to turn from a gas to a liquid to cool the air. This plays a vital role in ensuring that cold air blows from your air conditioning vents.
Conclusion
If you did find a small problem, you could fix it quickly; congrats! Now, we bet you want to ensure this doesn’t happen again. Through these causes, you can detect and solve your problem. We will be glad that you read this article.
