Troubleshooting
AC Not Cooling: Causes, Fixes and Repair Cost
The most common causes are a clogged filter, a dirty or iced evaporator coil, a failed capacitor and low refrigerant from a leak. Filter and airflow issues are homeowner-fixable; refrigerant and electrical faults are not.
Verified August 2026
Typical repair cost
$0–$6,000
Most likely cause
Clogged air filter restricting airflow
DIY-checkable steps
5
Why is my AC running but not cooling?
Clogged air filter restricting airflow
The most common causes are a clogged filter, a dirty or iced evaporator coil, a failed capacitor and low refrigerant from a leak. Filter and airflow issues are homeowner-fixable; refrigerant and electrical faults are not.
Safety first: Turn the system off at the thermostat and breaker before removing any panel. Refrigerant work requires EPA certification.
Likely causes and what each costs to fix
| Cause | Likelihood | Fix | Cost |
|---|---|---|---|
| Clogged air filter restricting airflow | Most common | Replace the filter and run the fan to thaw any ice. | $0–$40 |
| Failed run capacitor | Most common | Technician replaces the capacitor at the outdoor unit. | $150–$400 |
| Dirty condenser coil | Common | Coil cleaning and fin straightening. | $120–$350 |
| Low refrigerant from a leak | Common | Leak search, repair and recharge. | $350–$1500 |
| Frozen evaporator coil | Common | Thaw, correct airflow, then find the root cause. | $150–$600 |
| Failed compressor | Less common | Compressor or full system replacement. | $1500–$6000 |
What you can check yourself
- 1. Confirm the thermostat is set to COOL and below room temperature
- 2. Replace the air filter
- 3. Check the outdoor breaker and disconnect
- 4. Clear vegetation and debris around the condenser
- 5. Look for ice on the refrigerant lines — if present, shut cooling off and run the fan
When to call a professional
- • Ice keeps returning after a filter change
- • The outdoor fan hums but does not spin
- • You suspect a refrigerant leak
- • The breaker trips repeatedly