This one needs a licensed pro
Likely cause: low refrigerant or a failed part
If settings, filter, outdoor clearance and drain all check out, the remaining causes are inside the equipment. Turn the AC off and call an HVAC technician.
Why this happens
Carrier lists a refrigerant leak, electrical parts like the contactor or capacitor, the blower motor and the compressor among the causes of warm air, and This Old House adds a dirty or frozen coil. A hissing sound or oily residue near the unit or lines points to a refrigerant leak. The EPA says "only Section 608 certified technicians can purchase refrigerants intended for use with stationary refrigeration and air-conditioning equipment," and its rules prohibit venting refrigerant while servicing a system.
What to do right now
- Set the thermostat to Off. Carrier warns that running a malfunctioning AC can overheat the compressor and cause permanent damage.
- Leave the panels on the indoor and outdoor units closed. Don't try to add refrigerant or touch electrical parts.
- Keep a fan running or the windows open for comfort until the technician comes.
- Write down what you already checked so the technician doesn't repeat it.
- Carrier's AC blowing hot air page estimates repair costs typically range from $200 to $1,500 depending on the cause. That is Carrier's estimate, not a quote.
What to tell the HVAC technician
- The AC runs and the outdoor fan spins, but the air from the vents is warm.
- Any hissing sound, oily residue, or ice you noticed, and where.
- That the thermostat, filter, outdoor clearance and drain all checked out.
- The brand, model and serial from the outdoor unit's data plate.
Build the full list: what to tell the HVAC technician.
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