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General homeowner information, prepared with AI assistance. An on-site professional must confirm the cause and appropriate repair.
Learn why your AC may not be cooling, including thermostat issues, dirty filters, low refrigerant, weak airflow and when to request service.
Leave the building immediately. For fire, a CO alarm or immediate danger, call 911 from outside. For a suspected gas leak, contact your gas utility from a safe location. Do not wait for an HVAC callback or try to restart the equipment.
Local gas and carbon monoxide emergency guidanceKey takeaways
- Check thermostat mode and setpoint before opening equipment
- A dirty filter can reduce airflow but is not the only possible cause
- Ice, breaker trips or burning smells require professional service
Common causes to consider
Several conditions can create a similar symptom. A technician confirms the cause with measurements before recommending repair.
- Incorrect thermostat settings or a failed thermostat call
- Restricted airflow from a dirty filter, blocked return or blower issue
- Outdoor condenser power, contactor, capacitor or fan problem
- Dirty indoor or outdoor coil
- Low refrigerant caused by a leak that must be located and repaired
Safe checks you can do first
Only check accessible controls and filters as directed by the equipment manual. Do not open electrical panels, handle refrigerant or bypass safety controls.
- Set the thermostat to Cool and lower the setpoint by several degrees
- Replace a visibly dirty filter with the correct size
- Confirm supply and return vents are open
- Look for ice, standing water or a tripped breaker without repeatedly resetting it
When the problem is urgent
For gas odor, a CO alarm, smoke or immediate danger, follow the emergency guidance above. For other equipment faults, stop using the system when safe and contact an HVAC professional:
- The breaker trips again after one reset
- You smell burning or see damaged wiring
- The indoor coil or refrigerant line is covered in ice
How to reduce repeat problems
- Schedule cooling maintenance before peak heat
- Keep vegetation and debris away from the outdoor unit
- Record filter size and replacement dates in your account
Related professional service
See our Air Conditioning Repair page for symptoms, diagnostic steps and service-request options.
