An air conditioner has one primary job: to blow cool air through the home. So when an AC blows warm air through the home, it is a sign that something is wrong with your HVAC system. That’s the bad news. The good news is that many causes of an AC blowing warm air are easy enough for homeowners to troubleshoot.
Key Takeaways
- Common causes of an AC blowing warm air that most homeowners can resolve include clogged air filters, tripped circuit breakers, thermostat issues, dirty condenser coils, and dirty evaporator coils.
- Other common causes of an AC blowing hot air that require a licensed HVAC technician include refrigerant leaks, frozen evaporator coils, electrical problems, and compressor failures.
- Sometimes it makes more financial sense to replace an AC unit rather than repair it, especially if AC repair costs exceed replacement costs.
- Preventive AC maintenance, especially seasonal AC tune-ups, can help prevent costly repairs and extend equipment lifespan.
Quick AC Troubleshooting for Homeowners
While HVAC problems are never fun, oftentimes there is a simple explanation for the issue and an equally simple fix.
Check Thermostat Settings
The problem: Sometimes the thermostat simply isn’t at the right setting, which gives your AC unit the wrong signals. Other times, its battery dies.
The signs: The thermostat is set to Heat rather than Cool, the thermostat is set to Auto instead of On, or the thermostat has no display settings can all indicate that your thermostat is the cause of the hot air.
The solution: Use your thermostat manual to change your system to the correct settings (e.g., Cool instead of Heat or On instead of Auto) or check if the battery needs replacing.
Inspect the Air Filter
The problem: A dirty air filter means your system has to work harder to push cool air through the home and can lower indoor air quality.
The signs: Energy bill spikes and clear dirt on the filter can indicate a clogged air filter.
The solution: Replace the filter.
Check the Circuit Breaker
The problem: Circuit overloads and ground faults can trip the home’s circuit breaker, messing with the AC unit’s settings or even turning it off entirely.
The signs: If other appliances or electrical fixtures in the house don’t work, it may indicate a tripped breaker.
The solution: Locate the circuit breaker, find the switch that connects to your HVAC unit, and flip it back to On.
Assess the Interior Evaporator Coils
The problem: Inside the home’s air handler are the evaporator coils; they work in tandem with the condenser coils to exchange heat between the interior and exterior of the home. If the coils become dirty or freeze, it can mean only uncooled air passes through the system.
The signs: Bad smells along with poor or warm airflow can indicate dirty evaporator coils.
The solution: If the evaporator coils are dirty, shut off the system before gently cleaning the coils and removing the fallen dust and dirt. If the evaporator coils are frozen, turn off the system and contact an HVAC professional (see more below).
Examine the Outdoor Condenser Unit
The problem: The condenser unit, which sits outside the home, houses HVAC components that release heat from the home to the outdoors. It includes the AC compressor, condenser fan, and condenser coils.
The signs: Notable signs of dust or debris are caught on the unit’s paneling or interior coils and fan blades.
The solution: Disconnect the outdoor unit from its power source, then clear debris or dust from the coils and fan. If you believe the compressor is causing the problem, contact a professional (see more below).
Know When to Ask for Help
Minor issues are easy enough to resolve with basic troubleshooting. Critical failures, which can include the following, require the intervention of a certified HVAC technician.
Compressor Failure
The problem: The AC compressor is the heart of the system, meaning nothing can happen without it. In other words, if the compressor fails, the cooling process stops entirely.
The signs: Strange sounds, weak airflow, warm airflow, tripped breakers, and a completely malfunctioning system can indicate a compressor failure.
The solution: A compressor failure is a complex repair that requires professional HVAC expertise.
Refrigerant Leaks
The problem: Refrigerant does not “run out” like fuel; low refrigerant levels mean there is a refrigerant leak.
The signs: Hissing sounds or ice buildup on the copper lines are clear indicators of leaking refrigerant.
The solution: Handling refrigerant requires specialized licensing and equipment. Call a licensed HVAC company to address the issue.
Frozen Evaporator Coils
The problem: Frozen coils often result from restricted airflow or low refrigerant.
The signs: If you notice ice on the indoor unit or the copper pipes, your coils have frozen. Other signs of frozen evaporator coils include water leaks and a musty smell.
The solution: Turn the unit off immediately to allow it to thaw, then call for service.
Electrical Component Failure
The problem: Capacitors and contactors regulate the power flow to your compressor. These parts degrade over time due to heat and electrical stress.
The signs: If you hear a humming sound but the blower fan isn’t spinning, a capacitor has likely failed.
The solution: Handling electrical problems on your own is extremely dangerous (and illegal in some jurisdictions). Shut off electricity to the equipment and schedule service with an HVAC professional.
The Importance of AC Maintenance
The HVAC system keeps the home comfortable year-round. When it fails, the comfort and safety of the whole house is in jeopardy. That’s where consistent maintenance can help.
With a regular maintenance schedule, you reduce the odds of a costly breakdown, extend the life of your equipment, keep the home more comfortable, and boost system efficiency (which can lower energy bills).
Repair or Replace?
Sometimes AC issues are easy—and affordable—to fix. Sometimes they are not. Knowing when to replace and when to repair an AC unit can be one of the most cost-effective decisions homeowners can make.
When should you repair or replace an AC unit? As a general rule of thumb, consider the “5000 Rule”: multiply the age of the unit by the cost of the repair. If the total exceeds $5000, replacement is the more financially savvy decision.
Of course, the 5000 rule is just a guideline. Other times, even if the total is lower than 5000, it may still make sense to replace the entire unit. For example, if your system utilizes R-22 refrigerant (a phased-out substance), repairs involving the sealed system will usually be prohibitively expensive. Furthermore, modern systems offer significantly higher SEER2 (Seasonal Energy Efficiency Ratio) ratings, which can offer a return on investment through lower utility bills.
Restore Your Comfort Today
Your AC blowing hot air through the home is annoying, but it’s fortunately easy enough to fix at home with a few quick troubleshooting steps. But if these steps don’t work, it’s best to call a licensed and trained HVAC company to remediate the issue, so your home can get back to comfortable temperatures as quickly (and as safely) as possible.
FAQs
How can I fix my AC from blowing hot air?
To fix an AC from blowing hot air, you first need to diagnose the issue. To troubleshoot at home, you can check the:
- Thermostat to see if the settings are correct or if the battery needs changing,
- Air filter to see if it needs replacing,
- Outdoor condenser unit for clogged or dirty condenser coils and fan,
- Indoor evaporator coils for dirt buildup, and
- Circuit breaker for tripped switches.
If the issue is not resolved from these steps, it’s best to contact a licensed HVAC technician to diagnose and fix the issue.
What are common causes of air conditioners blowing hot air?
Common reasons an air conditioner will blow hot or warm air include:
- Clogged air filters
- Dirty evaporator coils
- Dirty condenser coils
- Thermostat issues
- Frozen evaporator coils
- Electrical problems
- Refrigerant leaks
- Compressor failure
Should I turn off my AC if it's blowing hot air?
Usually, yes, you should turn off the AC if it’s blowing hot air. Turning off the AC reduces unnecessary strain on the system and makes it safer to work with.
What is the 3-minute rule for air conditioning units?
The “3-minute rule” for AC units is a guideline that suggests waiting at least three minutes between turning an AC system off and turning it back on.
Can broken AC units cause sinus issues?
Yes, broken air conditioners may contribute to sinus issues by blowing dry, irritating air or allergens through the system.
