What is typically the first step in troubleshooting a furnace that does not reach the desired temperature?

When troubleshooting a furnace that is not reaching the desired temperature, starting with the power supply is critical because power issues can be a fundamental cause of many operational failures. If the furnace is not receiving power, it cannot function at all, which means it will not heat the home effectively. Confirming that the furnace is fully powered allows the technician to eliminate this common and straightforward issue before investigating more complex factors.

After ensuring that the power supply is dependable, other components such as the thermostat settings, air filters, and gas supply can be examined. Addressing these elements is essential, but if the furnace lacks power, none of those adjustments will have any effect. Therefore, verifying the power supply serves as a logical and efficient first step in the troubleshooting process.