Elevator Mechanic Practice Exam 2025 - Free Elevator Mechanic Practice Questions and Study Guide

Checking the door interlock as the first device in the case of a suspected phasing issue with building power is insightful, particularly because the door interlock can directly impact the safe operation of the elevator. If there's a phasing issue, it may lead to improper functioning of various components, including the door mechanisms. An interlock failure could potentially prevent the doors from operating correctly, which is essential for safe entry and exit from the elevator cab.

However, while the door interlock is important, focusing on the reverse phase relay gives a more immediate assessment of power issues. This relay is specifically designed to detect phase loss or reversal conditions. Therefore, checking the reverse phase relay before other components would typically be the most direct approach to diagnosing a phasing issue. It's crucial to ensure that the power delivered to the elevator system is correct and stable before addressing the functionality of auxiliary devices like door interlocks.