Why Is My Heat Pump Not Cooling on Hot Days?

A heat pump not cooling on hot days usually has an airflow blockage, low refrigerant, or a heat load beyond its capacity. The most common cause is a dirty filter or a clogged outdoor coil. On very hot afternoons, a unit sized for mild weather may run constantly and still hover in the upper 70s, which points to capacity or duct losses. We often see this around Lake Mary as humidity exposes weak ducts and marginal charge. If basics don’t help, book a diagnostic; treat urgency only for electrical or icing issues.

Quick checks you can do:

• Replace the air filter; fan on Auto.
• Clear debris around the outdoor unit; gently rinse coil.
• Verify Cool mode and setpoint below room temp.

If you see ice or smell burning, shut it off and call a pro. <br/> Updated: 2026-03-31 <br/> Need help in Lake Mary, FL? Call 407-584-1433 or book online.