What does a solid yellow light on the exterior of a PA5 car indicate?

A solid yellow light on the exterior of a PA5 car indicates that the PEHU (Pantograph Electrical Heat Unit) is activated in that car. This is critical information for operators and maintenance crews, as the activation of the PEHU suggests that the car's systems are engaged in heating the pantographs, which are essential for ensuring efficient conductivity and performance, especially in colder weather when the risk of ice formation increases.

Understanding the significance of this indication is vital for effective train operation and maintenance management. Properly monitoring the activation of the PEHU can prevent operational problems related to power supply and overall train performance. This knowledge ensures that the train can operate safely and efficiently under various conditions.