What component is typically checked when troubleshooting a furnace that fails to ignite?

When troubleshooting a furnace that fails to ignite, checking the pressure switch is crucial because this component plays a vital role in ensuring the safe operation of the gas furnace. The pressure switch monitors the airflow within the system; it confirms that the blower is functioning correctly and that there is adequate venting for the combustion process. If the pressure switch does not activate due to improper airflow or blocked vents, the furnace will not ignite as a safety precaution to prevent potential hazards such as gas leaks or improper combustion.

While the other components mentioned may also be relevant in a broader troubleshooting scenario, they do not directly correlate to the immediate ignition failure in the same way. For instance, thermostat settings determine whether the furnace should start based on room temperature, but if the pressure switch is not indicating that it is safe to proceed, the furnace will not light regardless of the thermostat’s settings.

Thus, focusing on the pressure switch first can quickly identify whether airflow is sufficient and whether it is safe to ignite the furnace, making it a key component in this specific troubleshooting case.