What is required to confirm the heater and defroster function correctly?

To confirm that the heater and defroster function correctly, it is essential to check that they work in all positions. This ensures that the system is functioning as intended across its entire range of settings. The heater should be able to provide heat at different levels and in various directions to appropriately warm the cabin and defog the windows. This verification is critical for the safety and comfort of the driver and passengers, especially in adverse weather conditions.

Merely testing in specific positions may not provide a comprehensive evaluation of the system's performance, as certain functions or settings could be malfunctioning while others appear to be working. Therefore, conducting checks across all positions ensures that both the heater and defroster can operate effectively when needed, contributing to optimal vehicle operation and safety.