Why does my furnace keep turning off?

A furnace that starts and shuts down may be responding to a safety control, losing flame, overheating from restricted airflow, failing to prove pressure, or receiving an unreliable thermostat signal. Check the thermostat and filter if safe, but do not keep resetting the system or bypass a limit switch. Note whether the burners light, how long the blower runs, and any diagnostic light pattern. If there is gas odor, smoke, an unusual flame, or a carbon-monoxide alarm, leave immediately and call emergency services or the utility.