Which statement about the hydraulic quantity readout is true?

• A. It is valid at all times
• B. It is valid only when the system is pressurized
• C. It is valid only when the system is depressurized
• D. It is never valid

Answer: (B)

Hydraulic quantity readouts are tied to the system’s pressure. The indicator relies on a sensor or transducer that uses hydraulic pressure to determine and display how much fluid remains in the circuit. When the system is pressurized, that relationship between pressure and fluid quantity is valid, so the readout accurately reflects the reservoir level. If the system isn’t pressurized, the sensor isn’t driven in the same way, and the readout can be unreliable or meaningless, which is why it’s considered valid only when the system is pressurized. The other options would imply the readout works independently of pressure or never works, which isn’t how these gauges are designed to operate.