Why Is My Heat Pump Not Cooling on Hot Days?

A heat pump may stop cooling on hot days when airflow, refrigerant charge, controls, or simple system overload prevent it from moving heat out of your home. The most common trigger is restricted airflow, which keeps the outdoor coil from dumping heat into the outside air.

Around Mishawaka, we often see heat waves combine with grass clippings around the outdoor unit to choke off airflow. A quick technician test: if the outdoor fan runs but the air blowing out the top feels barely warm, the coil isn’t rejecting heat and efficiency crashes. Low refrigerant from a leak, incorrect thermostat mode, or an electrical fault can also halt cooling. Same-day and emergency help is available when the system won’t recover after basic checks.

Try these simple checks before service:

• Replace a clogged filter and open closed supply/return vents.
• Gently rinse the outdoor coil from the outside-in with power off.
• Confirm thermostat is on Cool, set to Auto fan, and disable any conflicting schedules.
• If you see ice on refrigerant lines or hear hissing, power off and schedule repair.

Always cut power at the disconnect before cleaning or touching any HVAC components. <br/> Updated: 2026-03-31 <br/> Need help in Mishawaka, IN? Call (574) 367-8549 or book online.