CDL Combination Vehicles TestCombination Vehicle Air BrakesEasy
During a pre-trip inspection of a combination vehicle, you notice that the air pressure gauge shows 60 psi, and the low air pressure warning light and buzzer are active. What action should you take?
- AContinue driving, but monitor the gauge closely.
- BIncrease engine RPM to maximum to get the compressor to work faster.
- CImmediately stop driving and do not move the vehicle until pressure builds to a safe level.
- DPump the brake pedal rapidly to build pressure faster.
Show answer & explanationAnswer & explanation
Correct answer: C. Immediately stop driving and do not move the vehicle until pressure builds to a safe level.
If the low air pressure warning activates (typically below 60 psi), it indicates insufficient air pressure for safe braking. You must stop immediately and not move the vehicle until the pressure builds to a safe operating level (usually above 100 psi) to ensure you have full braking capability.
Why the other options are wrong
- A. Continuing to drive with low air pressure is extremely dangerous as you may lose braking capability.
- B. While increasing engine RPM helps build pressure, simply doing so and continuing to drive is unsafe; the primary action is to stop until pressure is safe.
- D. Pumping the brake pedal rapidly will deplete air pressure even faster, making the situation worse.
Low Air Pressure Warning Action
When the low air pressure warning light and buzzer activate (typically below 60 psi), the driver must immediately stop driving and not move the vehicle until pressure returns to a safe operating range.
- Indicates insufficient braking pressure.
- Requires immediate stop.
- Do not move until pressure is safe.
Memory trick: Low air, light and buzzer, means stop, no fuss, no flutter.