An air conditioner not blowing cold air but running, especially in summer can quickly turn your living space into an unbearable oven.
How does this happen? I mean, how is it running but still not blowing cold air? It’s very rare, don’t you think? It’s even more frustrating that as homeowners, all we can do are basic things like restarting the thermostat since it’s the part of the HVAC system that we know the most about. But sadly, the problem often goes beyond that.
As a trusted HVAC company with 25+ years of experience, we have written this blog post to give you the most common reasons why the air conditioner is not blowing cold air but is running.
In essence, air conditioners act like a closed-loop heat exchanger. A special refrigerant circulates throughout the system, changing between liquid and gas states to move heat.
Warm air gets drawn indoors and passes over a cold evaporator coil. The refrigerant absorbs heat from the air, transforming from a liquid to agas, cooling the air in the process.
This warmed gas travels outside to a condenser coil. Here, a fan blows hot air away as the refrigerant releases the captured heat, transforming back into a liquid. The cooler liquid then returns inside to repeat the cycle, providing cool air for your comfort.
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Cause: A dirty air filter traps dust and debris, reducing airflow over the evaporator coil. This coil absorbs heat from the air, and restricted airflow prevents proper heat transfer, leading to warm air blowing from the vents.
Solution: Check your air filter monthly and replace it when clogged or dusty. Look for filters with a MERV rating (Minimum Efficiency Reporting Value) appropriate for your needs. A higher MERV rating traps smaller particles but reduces airflow slightly.Â
Cause: Refrigerant is the lifeblood of your AC system, absorbing and releasing heat. Low refrigerant levels reduce the system’s ability to cool air. This can be caused by leaks or natural degradation over time.
Solution: Adding refrigerant is a job for a qualified HVAC technician. They can diagnose the leak, repair it if necessary, and recharge the system to the proper level. Do not attempt to add refrigerant yourself. It’s a pressurized system, and improper handling can be dangerous.
Cause: Restricted airflow, dirty filters, or low refrigerant levels can cause the evaporator coil to become too cold. This leads to moisture in the air freezing on the coil, further restricting airflow and preventing proper cooling.
Solution: Turn off the AC system and let the ice melt naturally. This can take several hours. Once thawed, replace the air filter and check for any underlying issues like low refrigerant. If the coil freezes again, call an HVAC technician for further diagnosis.
Cause: The condenser coil sits outside and releases heat from the refrigerant. Dirt, leaves, and debris can accumulate on the coil, hindering its ability to dissipate heat. This reduces the system’s cooling efficiency.
Solution: Turn off the AC and carefully remove any debris from the condenser coil with a soft brush or vacuum cleaner. Be gentle to avoid damaging the delicate fins. You can also spray the coil with a garden hose to remove stubborn dirt.
Cause: A malfunctioning thermostat might not be properly communicating with your AC system. It could be set incorrectly, have a faulty sensor, or be nearing the end of its lifespan.
Solution: Check the thermostat settings and ensure it’s set to “cool” at a desired temperature. If the issue persists, replace the batteries (if applicable) or replace the thermostat altogether. For complex thermostat problems, read our article about fixing a thermostat not working or consult an HVAC technician.
Cause: The compressor is the heart of your AC system. It pressurizes the refrigerant, allowing it to absorb and release heat efficiently. A failing compressor can significantly reduce the system’s cooling capacity.
Learn more with our article about AC Compressor Not Turning On.
Solution: Unfortunately, a failing compressor usually requires professional repair or replacement by an HVAC technician. Signs of compressor failure include unusual noises coming from the unit, warm air blowing constantly, or the AC unit tripping the circuit breaker frequently.
Armed with a basic understanding of how your HVAC system works and the typical troubles that could arise, you can take proactive steps to troubleshoot and address the problem.
Regular maintenance, prompt repairs, and professional assistance when needed will avoid situations like having an air conditioner not blowing cold air but running, and keep you cool and pleasant throughout the hottest months of the year.
If you lack experience in repairing AC systems, it’s best to contact AAC Heating and Air INC to quickly restore your AC system to its former performance. Don’t hesitate to call us; it will be a pleasure to help you!
