There are few things that are more frustrating than cranking up your air conditioner on a super-sunny, 110 degree day… only to feel warm air coming out of your vents. In Arizona, that’s not just uncomfortable, it can be an emergency.
If you are finding that your A/C is blowing more warm air that you’ve noticed before, don’t panic yet. In many cases, it’s something minor that you can troubleshoot yourself before calling in the calvary. But in other cases, it can be a sign your system needs professional attention.
Here are some of the most common reasons your air conditioner is blowing warm air and what you should do about it.
Your Thermostat Is Set Incorrectly
It may sound simple, like tech support asking if you have rebooted your computer, but it happens more often than you’d think. Someone in the house bumps up the thermostat without asking or at least telling, or maybe a recent power outage reset it to a default settings. Always make checking the thermostat settings your first go-to move before assuming there’s a major issue.
Make sure it’s set to Cool and not Heat or Fan. Along that same line, verify that the fan setting is on Auto rather than On. When the fan is set to On, it will run continuously. On that setting, when the system isn’t cooling it will simply be recirculating room-temperature air. If you have a programmable or smart thermostat, confirm that your schedule didn’t change unexpectedly after a Wi-Fi update or power interruption. If your thermostat uses batteries, check them and replace if needed. Low battery voltage often causes erratic behavior or loss of signal between the thermostat and the HVAC system.
Dirty Air Filters Restrict Airflow
One of the most common reasons for warm airflow is a clogged air filter. This can be especially true if you have a houseful of pets. When your filter is loaded with with dust and debris, air is unable to pass through efficiently. Also, keep in mind that big houses with multiple units will more than likely have more than one air return and filter. Be sure that you know where they all are and inspect them regularly.
A lack of adequate circulation can cause the evaporator coils to freeze. When coils freeze, the system can’t absorb the heat from the air properly, and you’ll end up with warm, or barely cool, air flowing through the vents. If you suspect the coils may have frozen, the fix is easy. Turn the system off, replace the air filter, and give the coils a few hours to thaw out. Once you restart it, check the vents to see if the air feels cooler.
Going forward, Inspect the filter monthly and replace it every 30 to 90 days, depending on how much the air condition or heat has been used. Lean towards once a month during Arizona’s extremely hot and dusty summer months. Use a sharpie to mark the date that you replaced it on last – time can go by faster than you think.
The Outdoor Unit Isn’t Running
Your A/C system has two main components – the indoor air handler and the outdoor condenser unit. If the indoor fan is blowing but the outdoor unit isn’t running, your system will not be able to remove the heat from the air, resulting in warm air circulating inside the house. Common causes may include: a tripped circuit breaker, especially after a storm or power surge; loose or damaged wiring; a blown capacitor, which is a part that helps the compressor and fan start; or a failed compressor
The fix: first, check your breaker panel and reset any tripped switches. If that doesn’t solve it, and you notice silence from the outdoor unit, it’s time to call in a professional. Working with high-voltage components can be extremely dangerous, and making an accurate diagnosis on the compressor or capacitor issues requires specialized tools.
Low Refrigerant Levels
Refrigerant is the lifeblood of your air conditioning system. It is the element that absorbs the heat and moisture from inside your home and releases it outside. If your system is low on refrigerant, it is unable to cool the air effectively. You’ll notice warm air blowing from the vents or may even see frost forming on the copper lines near your outdoor unit. Refrigerant doesn’t evaporate and just run out over time. When it runs low it means there’s a leak somewhere in the system. The most common leak points are with joints, connections, and coils.
The fix: there is nothing that you can do. Refrigerant issues must be handled by an experienced and licensed HVAC technician. They’ll accurately locate and repair the leak, then recharge the system with the correct refrigerant type and amount needed.
It is important to know that if your system still uses R-22 Freon, typically units that are pre-2010, that refrigerant was phased out in 2020. Replacement supplies are limited and it can be very expensive. In those cases, upgrading to a newer, more efficient system may be the smarter decision.
Dirty or Blocked Condenser Coils
The condenser coils in your outdoor unit release the heat that the system removes from inside the home. If those coils are caked with dust, leaves, or grime, the heat can’t dissipate properly and the system ends up recirculating warm air.
The fix: Turn off power to the outdoor unit and inspect it. Remove any debris that you see from around the base, and gently rinse the coils with a garden hose using low pressure. Never use a pressure washer as it can bend the fins and damage the coils. For best results, have an experienced technician clean and inspect the outdoor unit during your regular HVAC maintenance visit.
Airflow Issues Inside the Ducts
If your air ducts are leaking, disconnected, or poorly sealed, the cool air that the system produces could be escaping into your attic or walls before it ever reaches the vents. That leaves you with warm air and, unfortunately, higher energy bills.
The fix: Remove the vent and check the area of the duct that is in plain sight for obvious issues like loose joints or whistling noises that could indicate leaks. Consider having your ducts inspected and resealed by a professional which can significantly improve both comfort and efficiency. In Arizona homes, duct leaks are incredibly common due to the frequency of heat expansion and aging insulation.
A Faulty Compressor
The compressor is the heart of your A/C system. It pumps refrigerant through the coils and drives the entire cooling process. If it’s shot or failing, the system may blow warm air even if everything else appears to be running correctly.
The fix: Unfortunately, compressors are one of the most expensive HVAC components to replace. If your HVAC system is more than 10 years old, a failing compressor could be the deciding factor on whether to invest in a new system rather than continuing with repairs.
It’s Just Too Hot Outside
When the blazing Phoenix summer hits 115 degrees or higher, even a perfectly healthy air conditioner can struggle to keep up. Most HVAC systems are designed to maintain around a 20 degree difference between indoor and outdoor temperatures. So, if it’s 115°F outside, it’s just plain hot and the best you should expect is around 75°F inside.
That’s normal and not a sign of failure. The key is to help your system out. Just developing a few good HVAC habits can make a huge difference such as closing blinds on the sunny side of the house, avoiding cooking with the over during peak hours, and keeping filters clean.
When to Call the Pros
If you’ve checked your thermostat, filter, and breaker, but the air still isn’t cool, then it’s time to call an HVAC technician. Continuing to let a struggling system run can make the problem even worse – especially if frozen coils or low refrigerant are involved.
At Martin Air HVAC, we understand how urgent all cooling issues are in Arizona. Our certified technicians will arrive at your home ready to diagnose the problem quickly and honestly – whether it’s a minor fix or a deeper repair. We’ll explain your options clearly and get your home back to comfortable again as soon as possible.
Contact Martin Air today for fast, reliable A/C repair across the Phoenix East Valley.
Learn More About A/C Maintenance
3 Mistakes to Avoid For HVAC Maintenance
Everything You Need to Know About Air Conditioning Maintenance
Should You Really Have Your HVAC System Serviced Every Year
Why Air Sealing Your Home Beats Cranking the Thermostat