How do you test the low air pressure warning device during a pre-trip check?

• A.Turn the warning lamp switch on while the engine is running at idle
• B.Drain all air from the tanks first and then restart the engine
• C.Press the brake pedal once with the parking brake released
• D.Build normal pressure, shut the engine off, and fan the brakes by pumping the pedal until the warning light and buzzer activate before pressure falls too low

Why

Fanning the brakes lowers tank pressure in a controlled way so you can confirm the warning activates while there is still time to stop safely. The manual standard is that the warning must come on before pressure drops below 60 psi, so a device that stays silent during this test is defective.

Manual topic: Air Brakes - Brake Inspection · From the Air Brakes practice bank (AB-130).

Practice this subject as a full test

More Brake Inspection Steps & Defects questions

• During a pre-trip inspection of an air brake system, what is the main purpose of checking each brake component before driving?
• When you inspect rubber air hoses for the service brakes, which condition should be reported as a defect?
• What should brake drums (or discs) be checked for during an inspection?
• Which finding on brake linings makes the brake unsafe until it is corrected?
• After building air pressure to governor cut-out, turning the engine off, and making a full brake application, what does a continuing drop on the air gauge after the initial drop tell you?