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Universal Air Systems

Troubleshooting

AC Blowing Warm Air

Quick answer

Most common cause is low refrigerant from a leak. Don't keep running it — you'll damage the compressor. Other causes: thermostat set wrong, frozen indoor coil, dirty filter.

Common causes

  • Refrigerant leak

    urgent

    Charge low → compression efficiency drops → no cooling. The leak needs to be found and sealed, not just topped off.

  • Frozen indoor coil

    moderate

    Filter clogged → airflow drops → coil temp drops below freezing → ice blocks airflow entirely → warm air. Turn off, let thaw, replace filter.

  • Thermostat on HEAT or FAN

    easy

    Common 'oops'. Switch to COOL.

  • Outdoor unit not running

    moderate

    Walk outside. If the outdoor unit is silent while the indoor blower runs, you've lost the compressor or contactor.

  • Dirty outdoor coil

    easy

    Heat can't reject through a dust-and-cottonwood-clogged condenser → cooling drops. Spray with a hose.

DIY first

  • 1 Confirm thermostat is on COOL with a low setpoint.
  • 2 Replace filter.
  • 3 Walk outside and confirm outdoor unit is running and not iced up.
  • 4 Hose down the outdoor coil (gently).
  • 5 If indoor coil is iced, turn the system to OFF (not COOL) and let the blower run — ice melts in 1–3 hours.

Call us if:

  • The line set has visible ice or oil residue
  • Outdoor unit is silent
  • Air is warm even after replacing filter, hosing condenser, and giving it 24 hours

Related service

Air Conditioning Repair

Other symptoms in this category

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