What should you check before running a hydro elevator after the car is built?

Before running a hydro elevator after the car is built, it is essential to check the piston for debris. The hydraulic piston is a critical component of the elevator system, responsible for raising and lowering the car. If there is any debris present in or around the piston, it can lead to improper function or even cause damage to the hydraulic system. Ensuring that the piston is clear of any obstructions is vital for the safe operation of the elevator.

While examining other elements like the power supply, pylon level, and cables is indeed important for the overall functionality and safety of the elevator, the presence of debris in the piston is a more immediate concern that could directly affect the elevator's performance and safety during operation. Prioritizing the condition of the piston helps to prevent potential hydraulic failures that could arise from contamination.