Why is my AC blowing warm air?
The usual causes are a thermostat set wrong, a dirty air filter, a tripped breaker, a dirty or iced-up outdoor unit, or low refrigerant from a leak, and only the first few are safe for you to check.
Safe checks you can do first
- Thermostat. Make sure it is set to cool, set lower than the room temperature, and has good batteries. Lennox notes it may be accidentally set to heat.
- Air filter. Lennox says a dirty filter restricts airflow and can cause the system to overheat. Turn the system off, check the filter, and replace it if it is clogged.
- Breaker. Check the electrical panel for tripped breakers. Lennox says reset an HVAC breaker only once. If it trips again, call a technician.
- Outdoor unit. Remove visible debris like leaves and dirt from around the unit, and look for ice buildup or damage.
Causes that need a technician
Low refrigerant is often due to a leak. Lennox says a technician must diagnose and repair any leak before recharging the system, so you cannot simply top it off.
Lennox also says to call a certified technician if you see visible ice on the outdoor unit or refrigerant lines, if the AC turns on but never blows cold air, if it runs constantly without cooling, if you hear loud buzzing, hissing, or banging, or if the breaker keeps tripping.
Why a dirty filter keeps coming up
The Department of Energy says clogged, dirty filters reduce airflow and significantly reduce a system's efficiency. It recommends cleaning or replacing the filter every month or two during the cooling season.
If the AC is older
ENERGY STAR says to have a professional HVAC contractor evaluate equipment that is more than 10 years old or not keeping the house comfortable. See AC repair in Omaha or the repair or replace guide.
Get it looked at
If the safe checks do not fix it, a local contractor can quote the repair for free through this site. Use the link to get a free quote.
If the AC still blows warm air after these checks, request AC repair in Omaha.
Sources
Common questions
Why is my AC running but not cooling?
The same causes apply: thermostat settings, a clogged filter, a tripped breaker, a dirty outdoor unit, or a refrigerant leak. Lennox says to call a technician if it runs constantly without cooling.
Can I add refrigerant myself?
No. Lennox says a technician must diagnose and repair any leak before recharging the system.
Should I keep running the AC if it blows warm air?
Lennox advises turning the system off to check the filter. If you see ice on the outdoor unit or refrigerant lines, it says to call a professional.