Why Is My AC Running But Not Cooling? Common Causes and Fixes
True North Comfort SolutionsFounder, True North Comfort SolutionsDecember 5, 20255 min read
Check Your Air Filter First
A dirty or clogged air filter is the number one cause of AC performance issues and the easiest to fix yourself. When the filter is blocked, your system can't pull in enough air, which reduces cooling capacity. Check your filter and replace it if it looks dirty -- this alone fixes the problem about 30% of the time.
Thermostat Issues
Before assuming the worst, verify your thermostat is set correctly. Make sure it's set to "cool" mode (not "fan" or "heat"), the temperature is set below the current room temperature, and the batteries are fresh if it's a battery-powered unit.
Frozen Evaporator Coil
If you notice ice building up on the indoor unit or refrigerant lines, you likely have a frozen evaporator coil. Turn the system to "fan only" mode to let it thaw, then check for restricted airflow (dirty filter, blocked vents, closed dampers). If it refreezes, you need a professional diagnosis.
Low Refrigerant
Low refrigerant is a common cause of poor cooling, but it's not something you can fix yourself. Refrigerant doesn't get "used up" -- if it's low, you have a leak somewhere. A qualified technician needs to find and fix the leak, then recharge the system to the proper level.
When to Call a Professional
If you've checked the filter and thermostat and the problem persists, it's time to call a professional. Continuing to run a system that's not cooling properly can cause additional damage. A diagnostic service call ($59-$99) will identify the exact issue, and the fee is waived if you approve the repair.
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Frequently Asked Questions
Why is my AC blowing warm air?
Common causes include a dirty filter, low refrigerant, a frozen evaporator coil, or a failing compressor. Start by checking your filter and thermostat settings, then call a professional if the issue persists.
How much does it cost to fix an AC that's not cooling?
It depends on the cause. A filter change costs under $20. Common repairs like capacitor replacement or refrigerant recharge typically range from $149-$399. Our diagnostic fee ($59-$99) is waived if you approve the repair.
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