Illinois CDL Practice Exam

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Prepare for the Illinois CDL Exam. Study with flashcards and multiple-choice questions, complete with hints and explanations. Boost your confidence and get ready to pass your CDL exam!

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What triggers the visibility of a mechanical arm in the "Wig Wag" device in an air brake system?

  1. Increased air pressure

  2. Brake pedal application

  3. Air system pressure below 60psi

  4. Spring brake engagement

The correct answer is: Air system pressure below 60psi

The visibility of a mechanical arm in the "Wig Wag" device is triggered when the air system pressure drops below a certain threshold, typically around 60 psi. The Wig Wag is designed to alert the driver when the air pressure is insufficient for safe operation. When the pressure falls below 60 psi, the mechanical arm rises, indicating a warning condition. This safety mechanism is crucial as it helps prevent unsafe operation of the brakes due to insufficient air pressure, which could lead to brake failure. Drivers must pay attention to the Wig Wag's warning to ensure they maintain proper air pressure levels in their braking system, which is essential for effective braking performance.

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