In what situation would the voltage between L and M be significant?

The voltage between L (line) and M (motor or load) is particularly significant during normal operation with closed contacts because this is when the system is actively functioning and drawing power. In this state, the components such as the compressor and other electrical parts are energized, and the voltage present serves to ensure they are operating as intended.

When contacts are closed in a circuit, it allows current to flow, providing power to the connected equipment, which is essential for the system's operation. Monitoring the voltage during this phase can help technicians diagnose if the system is performing properly, as any fluctuations or deviations from expected voltage can indicate potential issues.

In contrast, during the startup of the compressor, the voltage might spike momentarily, but it’s not stable enough to assess overall system performance. In standby mode, the voltage can be present but doesn't indicate active system function. While testing for shorts is crucial, it typically involves short sections of the circuit where detailed voltage readings might not represent the overall operational status as clearly as during normal conditions.