Why Is My AC Not Cooling?
The most common causes of an AC not cooling are a dirty air filter, low refrigerant, dirty condenser coils, or frozen evaporator coils. Start by checking your filter, this fixes over 30% of AC problems. If the filter is clean and the issue persists, you likely need professional diagnosis.
Common Causes
Dirty Air Filter
A clogged filter restricts airflow, forcing your AC to work harder while delivering less cooling. In Phoenix's dusty environment, filters can clog in 2-4 weeks during heavy use. This is the #1 cause of AC problems.
Low Refrigerant
If your system is low on refrigerant, it can't absorb heat effectively. Refrigerant doesn't get 'used up', if it's low, you have a leak that needs repair. You may notice ice on the refrigerant lines.
Dirty Condenser Coils
The outdoor unit's coils release heat from your home. When covered with dust, dirt, or debris, they can't release heat efficiently. Phoenix's dusty environment and monsoon season accelerate this buildup.
Frozen Evaporator Coils
Ice on the indoor coils blocks airflow and cooling. This is usually caused by low refrigerant, poor airflow (dirty filter), or a failing blower motor. Don't chip ice off, you can damage the coils.
Thermostat Issues
Sometimes the problem is the thermostat, not the AC. Batteries may be dead, it may be set incorrectly, or the thermostat itself may be malfunctioning and not calling for cooling.
Undersized System
On Phoenix's hottest days (115°F+), even properly working ACs struggle. But if your system can never keep up, it may be undersized for your home. This is common in homes with additions or upgraded windows.
What Should You Do?
Try This First
- Check and replace your air filter if dirty (this fixes 30%+ of problems)
- Verify thermostat is set to COOL and temperature is below current room temp
- Make sure all supply vents are open and unobstructed
- Check that the outdoor unit is running and the area around it is clear
- Look for ice on the refrigerant lines, if present, turn off AC and call for service
Call a Pro If...
- AC runs constantly but can't reach set temperature
- You see ice on refrigerant lines or the outdoor unit
- The outdoor unit isn't running but the indoor fan is
- You've changed the filter and checked obvious issues with no improvement
- There's a significant temperature difference between rooms
- Your energy bills have suddenly spiked