The room has reached its set temperature, but air is still coming from the vents. Before assuming the air conditioner has failed to shut off, look for a separate setting marked Fan. It controls a different part of the system from the Heat or Cool selector.

Two controls, two different jobs

The temperature setting tells the system when heating or cooling is needed. The fan setting controls circulation through the ductwork. Selecting Fan ON does not, by itself, tell the air conditioner to keep producing cold air.

Honeywell Home explains that AUTO operates the fan with a heating or cooling call, while ON keeps the fan running continuously. Some models also offer a circulation setting that runs the fan intermittently. Check your own manual for its timing rather than assuming every thermostat behaves alike.

A useful comparison at the thermostat

• AUTO: A starting point when you want fan operation tied to heating and cooling demand.
• ON: Continuous air movement, including periods when the system is not actively heating or cooling.
• CIRC or a fan schedule: Model-specific circulation periods; review the schedule as well as the main switch.

Do not confuse Fan AUTO with an automatic Heat/Cool mode. Similar labels can appear in different menus. Read the label above the control before changing it.

Try an observation, not a guessing game

Take a photo of the current settings. Note the room temperature, target temperature, operating mode and fan selection. If the fan is ON, select AUTO according to the manual and observe a normal cycle without repeatedly changing the temperature.

An example: the thermostat displays 74°F, the cooling target is also 74°F, and Fan ON is selected. Continued airflow alone is not evidence that cooling is still running. A second observation matters: is the home maintaining the chosen temperature?

Record what changes after selecting AUTO. If air keeps moving, check for a programmed circulation period and any normal fan delay described in the manual. Avoid opening equipment panels to investigate controls.

When the fan switch is not the whole problem

If the home stays too warm, use our AC running but not cooling checklist. If only one room is uncomfortable, our room-to-room airflow guide addresses a different problem from thermostat selection.

For a service call, share the settings photo and explain whether the airflow continued during AUTO, ON or a scheduled fan period. That is more useful than reporting only that “the AC never stops.” Leave wiring and internal control checks to a technician.

For everyday programming, see our thermostat scheduling guide and the wider HVAC resource hub.