What is a common method for troubleshooting a furnace that won't start?

Checking the thermostat settings is a fundamental step in troubleshooting a furnace that won't start. The thermostat acts as the control center for the heating system, determining when heat is needed based on the temperature of the home. If the thermostat is set incorrectly—such as being turned off, set to a temperature lower than the current room temperature, or malfunctioning—it can prevent the furnace from receiving the signal to ignite and operate.

By ensuring that the thermostat is set to a proper temperature and functioning correctly, you can quickly determine whether the issue lies within the thermostat itself or if further investigation is needed. This step is often the simplest and quickest to check, making it a common starting point for troubleshooting furnace issues.