What could indicate a Critical Defect when illuminated?

A pneumatic friction brake system being illuminated as a critical defect suggests that there are significant issues regarding the braking mechanism of the machinery or vehicle. The pneumatic braking system is crucial for halting the movement of a vehicle, and any defect in this system could compromise safety. An illuminated indicator associated with the combustion or function of the pneumatically actuated brakes implies that the brakes may not be functioning as intended, which could lead to severe consequences like loss of control or difficulty in stopping.

In contrast, while defective sanders, low power supply to the cabin, and failing lights in the passenger area can present their own issues, they do not pose an immediate and severe risk to the operational safety of the vehicle. Defective sanders might affect sand distribution for traction, but this is not as critical as brake malfunction. A low power supply to the cabin might impact comfort or functionality within the cabin but would not directly affect the ability to control or stop the vehicle. Failing lights in the passenger area could lead to visibility issues, but they do not endanger the fundamental safety of operations like a brake system issue does. Hence, identifying a critical defect in the pneumatic friction brake system is vital for ensuring safety during operation.