CDL Practice Question #154

In a fully charged dual air-brake system at idle, you should test the low-pressure warning by:

Letting the air bleed down with the engine off and brakes off, fanning the brakes if needed; warning should activate at or before 60 psi
Holding the foot valve down for one minute
Removing the alternator belt
Disconnecting the compressor

Correct. Engine off, fan the brake pedal to bleed pressure. The low-pressure warning device should activate before pressure drops below 60 psi.

Why this question matters

This question is one of 71 in our Air Brakes bank. The reasoning above comes directly from the AAMVA CDL Manual, the source document used by every U.S. state DMV. Memorizing the underlying rule — not just the letter answer — is what separates passing on the first attempt from a return trip and another fee.

Practice more

Full Air Brakes practice test
Air Brakes study guide
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