Why Is My Heat Pump Not Cooling on Hot Days?

A heat pump that won’t cool on hot days usually has restricted airflow, a refrigerant issue, or a thermostat/control problem. The most common culprit is airflow: a clogged filter or a dirty outdoor coil keeps heat from moving out of your home. Low refrigerant from a leak can also reduce cooling, and control settings can force the system to run but not actually cool. In our Martinsville service area, we often find an outdoor coil that looks clean from the top yet is packed with lint deep in the fins.

Try these quick checks before calling:

• Replace a dirty air filter and clear debris from the outdoor unit
• Confirm the thermostat is on Cool, set below room temp, and Fan is Auto
• Look for ice on the refrigerant lines or a tripped breaker/float switch
• Note short cycling or warm supply air under load

If you see ice or repeated breaker trips, turn the system off and schedule service. <br/> Updated: 2026-04-04 <br/> Need help in Martinsville, IN? Call (812) 269-5994 or book online. “We are extremely pleased with our new high-efficiency heat pump.” — Mark C.