During a pre-operational inspection on a MEP 12, the voltage regulator switch should be in which position?

The voltage regulator switch should be in the "Auto" position during a pre-operational inspection on a MEP 12. This setting ensures that the voltage regulation system is automatically controlling the output voltage of the generator as intended. When in auto mode, the system continuously monitors the generator's performance and adjusts the voltage output to maintain a stable electrical supply, which is crucial for equipment safety and efficiency during operation.

In contrast, if the switch were set to "Manual," it would require operator intervention for any adjustments, potentially leading to unstable voltage levels and risking damage to connected equipment. Setting the switch to "Off" would disable the voltage regulator entirely, preventing the unit from properly managing voltage output. The "Test" position is typically used for diagnostic purposes and is not suitable for standard operational readiness. Therefore, "Auto" is the correct position for ensuring the generator is ready to operate safely and efficiently.