Why Is My AC Running But Not Cooling The House?

An AC that runs but doesn’t cool usually has one of four issues: blocked airflow, lost heat transfer, control problems, or duct/insulation losses. The most common cause is a clogged air filter or a dirty outdoor coil that chokes airflow so the system can’t move heat out of your home. Low refrigerant from a leak, a failing capacitor or fan, incorrect thermostat settings, or leaky ducts can also keep air moving but not getting cold. We often see this around the Denver metro, including Commerce City, when cottonwood fluff mats over outdoor condensers after the first heat wave.

Try these quick checks before calling:

• Replace a dirty filter and confirm supply vents are open.
• Set thermostat to Cool, Fan Auto, and a target at least 5°F below room temp.
• Clear leaves and lint within 2 feet of the outdoor unit.
• If you see ice on lines or coil, turn AC off and run Fan to thaw.

Avoid running an iced or short-cycling system to prevent compressor damage.

Updated: 2026-10-26

Need help in Commerce City, CO? Call (720) 994-7055 or book online. “Nathan arrived on time and within an hour replaced parts and had heat running in our house. Very clean and professional! Highly recommend!” — Brian T.