What should I do if my AC is blowing warm air intermittently?

For an AC blowing warm air on and off, check the thermostat mode, air filter, and breakers first, then schedule a professional diagnosis if it continues. The most common cause is restricted airflow that ices the coil; as it thaws, the air turns cool again, then warms—this cycle can repeat. A partially iced coil can re-cool briefly after a thaw, which is why the symptom feels random. If you see ice on your refrigerant lines or the coil, your system needs to be serviced. Often that's a sign of a refrigerant leak. Our technicians in Wentzville and surrounding areas often find clogged drain safety switches and dirty outdoor coils during humid stretches. If you do need a repair, our Preferred Partner Plan saves 15% and includes two system checks starting at $19/month. If breakers trip repeatedly or you smell burning, treat it as urgent; we’re available 24/7.

• Set thermostat to Cool and Auto; replace a dirty filter.
• Make sure the outdoor unit runs and has clear airflow.
• If you see ice on lines or the indoor coil, turn AC off and let it thaw.
• Check for a full condensate pan or tripped float switch; clear the drain.

Call a pro if warm-air cycles return after these checks.

<br />

Updated: 2026-02-13

<br />

Need help in Wentzville, MO? Call 3148148455 or book online. “Air Comfort is easy to work with, reliable and efficient.” — Jacqueline G.