For a high-efficiency furnace that won't energize the blower motor after the preselected time, what is the most appropriate troubleshooting procedure?

In a high-efficiency furnace that is experiencing issues with energizing the blower motor, measuring voltage to the motor and testing the run capacitor is a critical troubleshooting procedure. This is because the blower motor relies on both proper voltage and a functional capacitor to operate correctly.

When voltage is applied to the motor, the run capacitor helps to start the motor and ensures that it runs efficiently. If the motor is not receiving the correct voltage, it may not start at all. Similarly, a faulty run capacitor can prevent the motor from operating, leading to insufficient airflow and possible overheating situations. Thus, testing both aspects gives an accurate diagnosis of the motor's operational readiness.

Inspecting the gas valve for leaks, checking the room temperature, or testing the thermostat settings, while they are useful steps in other scenarios, are not directly related to addressing the specific issue of the blower motor not energizing after a designated time. Each of those components can affect furnace operation but are less relevant when troubleshooting the immediate issue of motor activation.