When your air conditioner runs but blows warm air, the most common causes in Arizona are a failed capacitor, a bad contactor, a clogged filter, a frozen coil or low refrigerant from a leak. Start by checking your thermostat and filter. If the outdoor unit is not running or is humming, turn the system off and call for service.
Quick checks you can do
- Make sure the thermostat is set to Cool and below room temperature
- Confirm the fan is on Auto, not On
- Replace a dirty filter
- Check the breaker panel for a tripped A/C breaker
- Make sure the outdoor disconnect switch is on
- Look for ice on the refrigerant lines
Common causes
- Failed capacitorThe most common summer failure. The outdoor fan or compressor cannot start.
- Bad contactorThe switch that powers the outdoor unit burns out or sticks.
- Low refrigerantCaused by a leak. The system cannot absorb enough heat.
- Frozen coilIce blocks airflow; see our AC Freezing Up guide.
- Dirty condenser coilThe outdoor unit cannot release heat efficiently on 110°F days.
When to call
If the outdoor unit hums but the fan does not spin, turn the system off to protect the compressor and call us. A capacitor replacement typically costs $150 to $450 and is often a same-visit fix. And there is never an extra charge for nights, after-hours or weekends.
Related prices
| Service | Typical Price Range |
|---|---|
| Capacitor Replacement | $150–$450 |
| Contactor Replacement | $175–$400 |
| Refrigerant Leak Repair | $400–$1,500 |
| Condenser Coil Cleaning | $125–$300 |
Typical ranges for guidance only; your exact price is given in writing before any work begins. See our full price guide.