Quick answer
- Check the thermostat first: cooling mode, setpoint below room temperature, fan on AUTO not ON.
- A severely clogged filter or a frozen indoor coil can make vents blow warm.
- A tripped breaker or a failed capacitor on the outdoor unit means the condenser isn't running.
- Refrigerant leaks and compressor issues need a licensed technician — no safe DIY here.
Rule these out before you call anyone
- Thermostat set to COOL, setpoint at least 3° below current room temperature.
- Fan set to AUTO. On ON, the blower runs between cooling cycles and pushes room-temperature air through the vents — which feels warm.
- Air filter: if it's caked, replace it and give the system an hour.
- Breaker panel: look for a tripped breaker for the condenser or air handler. Reset once. If it trips again, stop and call — repeated resets can damage the compressor.
- Outdoor unit: is the fan spinning? Is the coil packed with cottonwood fluff or dirt?
The frozen-coil trap
If airflow is weak and the air is warm, check the copper lines at the outdoor unit or the indoor coil panel for frost. A frozen evaporator coil blocks airflow almost completely, and running the system harder makes it worse.
Freezing is a symptom, not a cause — the usual culprits are a filthy filter, a failing blower motor, or low refrigerant from a leak. Turn the system OFF and the fan to ON to thaw it (this can take several hours), then have the underlying cause diagnosed. If it froze once, it will freeze again.
What the technician checks next
- Capacitor and contactor on the outdoor unit — the most common electrical failures in hot weather.
- Refrigerant pressures and temperatures to identify leaks or restriction.
- Compressor amp draw and windings.
- Ductwork for disconnections — in some homes, cooled air is literally dumping into the attic or crawlspace.
When it's an emergency
Loss of cooling during a triple-digit inland heat wave is a health issue, especially for older adults, infants, and anyone with respiratory conditions. Family Maintenance Plan members have 24/7 emergency access; we also take emergency calls from non-members and dispatch as quickly as availability allows.
When you're ready