What maintenance fault has a unit number but does NOT have its own light?

The answer identifies a compressor fault as the maintenance fault with a unit number but does not possess its own indicator light. In many mechanical and electrical systems, such as those used in Siemens equipment, compressor faults are critical to monitor due to their impact on overall system performance. While these faults may be logged or referenced by a unit number in the diagnostic system, they often rely on the overall system indicators or failure messages rather than having a dedicated light for each specific fault.

In contrast, other faults listed, like TCU faults or CCTV failures, typically have dedicated indicators or alarm systems that provide immediate visual feedback about their status and any necessary actions to be taken. This distinction highlights how various components are monitored within fault detection systems, emphasizing the importance of understanding which faults may not have immediate visual feedback but are still crucial for system operation and maintenance.