It's one of the most common summer calls we get in Nashville: "My AC is running but it's not cooling." Here are the 7 most common causes — starting with the ones you can check yourself.
1. Clogged Air Filter
Most common cause. A severely clogged filter restricts airflow so the system can't cool. Check and replace your filter first.
Fix it yourself: Replace the filter. Nashville's pollen season means filters clog faster than the 90-day guideline suggests.
2. Low Refrigerant (Leak)
AC doesn't use up refrigerant — if it's low, there's a leak. Signs: ice forming on lines, hissing sound, system runs constantly without cooling. Requires a licensed technician.
3. Frozen Evaporator Coil
Caused by restricted airflow (dirty filter) or low refrigerant. Switch to "fan only" for 2–4 hours to thaw, then replace the filter. If it freezes again, call us.
4. Dirty Condenser Coils
Nashville pollen and cottonwood coat outdoor condenser fins by June. A coated condenser can't release heat. Gentle garden hose rinse (inside-out) can help.
5. Failed Capacitor
Most common AC failure in Nashville. Capacitor failure prevents the compressor or fan from starting. Signs: outdoor unit humming but fan not spinning. Quick, affordable same-day fix ($150–$300).
6. Compressor Issues
Everything else runs but no cooling occurs. Major failure — on older systems, often leads to full system replacement.
7. Thermostat Set to Fan Only
Check thermostat is set to COOL (not just FAN). Check temperature setpoint. Check batteries.
What to Check First
- Replace the air filter
- Thermostat set to COOL, fan to AUTO
- Check circuit breaker
- Look at outdoor unit — is the fan spinning?
- If none resolves it — call (615) 219-9882