What should be the air flow temperature when conducting a PDI on RV furnaces?

The correct choice highlights that the air flow temperature should be warmer than ambient temperature when conducting a Performance Diagnostic Inspection (PDI) on RV furnaces. This is important because the primary aim of the PDI is to evaluate how effectively the furnace generates and distributes heat. By ensuring the air flow temperature is warmer than the ambient environment, technicians can accurately assess the furnace’s performance, including its efficiency and the proper functioning of its heating elements.

If the air flow temperature is at or cooler than ambient, it could indicate that the furnace is not adequately heating the air or that there is an issue with the combustion process, heat exchanger, or overall airflow, which are critical aspects of the furnace's operation. Thus, measuring air flow that is warmer than the surrounding ambient temperature provides the necessary conditions to diagnose the furnace effectively.