How long should you generally wait after startup for air pressure to build from a low level to a safe operating level, as part of checking compressor performance?

Pick an answer

1. About 45 seconds or less to reach a full operating pressure, per typical manufacturer guidance, or as specified for your vehicle
2. Build-up time is not something drivers check during a pre-trip
3. Air pressure should build to full operating level within seconds no matter the outside temperature or altitude
4. Only the parking brake pressure needs to build; service brake pressure is irrelevant

Correct!

Not quite. The correct answer is highlighted.