AC Not Cooling / Not Blowing Cold Air

Common Symptoms

You might be experiencing this problem if you notice any of these signs:

• AC unit runs but air from vents is warm or not cold
• Room temperature not dropping despite AC running
• Outdoor unit running but indoor air not cooling
• Weak airflow with lukewarm air
• AC worked fine yesterday but not cooling today
• Fan blowing but no cold air
• Ice buildup on indoor coil or refrigerant lines
• Outdoor coil covered in dirt or debris
• Thermostat shows lower temperature but room still hot
• AC cools slightly then stops getting colder

Step-by-Step Diagnosis

Follow these steps to identify the exact cause of your problem:

1. Check thermostat set to COOL mode and 5°F below room temp
2. Verify outdoor unit is running (fan spinning, compressor humming)
3. Inspect air filter - replace if dirty or clogged
4. Check all vents are open and unobstructed
5. Feel outdoor unit - should be hot if working properly
6. Look for ice on indoor coil or copper lines
7. Check outdoor coil for dirt, debris, or bent fins
8. Verify both indoor and outdoor units have power
9. Listen for unusual sounds from compressor
10. Check for warm air blowing from outdoor unit
11. Measure temperature difference at supply vs return vents
12. Note how long ago system was last serviced

Most Common Causes (Ranked by Likelihood)

DIY Solutions

Step-by-Step Instructions:

1. Replace air filter immediately if dirty
2. Turn off AC and check for ice on indoor coil
3. If frozen, turn off AC for 3-4 hours to thaw completely
4. Clean outdoor condenser coil with garden hose (turn off power first)
5. Remove debris, leaves, and obstructions from around outdoor unit
6. Straighten bent condenser fins with fin comb
7. Ensure all supply vents throughout home are fully open
8. Check return vents not blocked by furniture or curtains
9. Verify outdoor unit has 2 feet clearance on all sides
10. Clean or replace indoor coil if accessible
11. After thawing, turn AC back on and monitor for 30 minutes
12. Measure temperature drop at vents (should be 15-20°F cooler)
13. If no improvement after cleaning, call professional for refrigerant check
14. Consider upgrading thermostat if AC is 10+ years old

When to Call a Professional

Don't attempt DIY repairs if you experience any of these situations:

• No temperature drop after filter and coil cleaning
• Ice keeps forming on coil repeatedly
• Hissing sound indicating refrigerant leak
• Compressor not running or making grinding noises
• Unit worked fine until sudden loss of cooling
• Temperature drop at vent less than 15°F
• Outdoor unit not getting hot during operation
• Age of system over 12 years with declining performance
• Multiple rooms not cooling despite open vents
• Burnt smell or electrical issues

Prevention Tips

Stop this problem before it starts with these preventive measures:

• Replace air filters every 30-90 days during cooling season
• Schedule annual AC tune-up before summer
• Clean outdoor coil with hose twice per cooling season
• Keep 2-3 feet clearance around outdoor unit
• Trim bushes and vegetation away from condenser
• Install programmable thermostat to reduce strain
• Shade outdoor unit if in direct sun
• Address refrigerant leaks immediately when found
• Seal ductwork in attic and crawlspace
• Upgrade insulation to reduce cooling load