Why Is My Heat Pump Not Cooling on Hot Days?

A heat pump may not cool on hot days because of airflow restrictions, low refrigerant, control problems, or a system that’s undersized or overdue for maintenance. The most common culprit is a clogged filter or dirty outdoor coil that chokes airflow and drops cooling capacity. Our technicians often see this during Long Island heat waves when systems run nonstop.

Watch for these specific signs that call for a pro check:

• Weak airflow or warm air from vents
• Outdoor unit running but the home keeps heating up
• Ice forming on the refrigerant lines or outdoor coil
• Thermostat set to cool but the system short cycles

Replace a dirty filter and clear debris around the outdoor unit; if performance doesn’t rebound, schedule a diagnostic (Gold Star’s $179 visit is waived with repair), and use emergency service if there’s no cooling in extreme heat. Turn the system off if you see ice or hear grinding to prevent damage. <br/> Updated: 2026-04-02 <br/> Need help in Jericho, NY? Call (516) 200-4014 or book online.