If your AC is blowing warm air, the most common causes are a thermostat set to the wrong mode, a dirty air filter, a frozen evaporator coil, low refrigerant from a leak, a tripped breaker on the outdoor unit, or a failed capacitor. Set the thermostat to cool, replace the filter and confirm the outdoor unit has power; if it still blows warm, call for same-day AC repair before the compressor is damaged.
Common causes
- Thermostat set to heat, on, or fan instead of cool/auto
- Dirty air filter choking airflow
- Frozen evaporator coil
- Low refrigerant from a leak
- Tripped breaker or disconnect at the outdoor unit
- Failed capacitor or contactor
Steps to try, and when to call us
- Set the thermostat to cool and lower the temperature.
- Replace the air filter if it is dirty.
- If the indoor coil is iced, turn the AC off and the fan on to thaw.
- Check the breaker and the outdoor disconnect for power.
If it still blows warm, trips the breaker, or freezes again, call First Response for same-day AC repair across San Antonio, 24/7.
Frequently asked questions
Why is my AC blowing warm air at night only?
Often low refrigerant or a weak capacitor that struggles as the unit cycles. It usually points to a failing part that should be checked.
Is warm air always low refrigerant?
No. A dirty filter, frozen coil, wrong thermostat setting or a tripped breaker are just as common, which is why we diagnose on-site.
How fast can you come?
Same day, 24/7. AC failures in San Antonio heat are emergencies.