CDL General Knowledge TestCombination Vehicles (if applicable)Hard
During a pre-trip inspection, a driver finds that the red (emergency) glad hand on the tractor is leaking air when disconnected from the trailer. What does this indicate?
- AA problem with the trailer's emergency brake system, not the tractor.
- BA faulty emergency air valve on the tractor, requiring repair.
- CA leak in the service air line, requiring replacement of the blue glad hand.
- DA normal condition, as the emergency line should leak when disconnected.
Show answer & explanationAnswer & explanation
Correct answer: B. A faulty emergency air valve on the tractor, requiring repair.
When the emergency (red) glad hand is disconnected, the emergency air line should be sealed by the tractor's emergency air valve, preventing air loss. If it is leaking, it indicates a fault in this valve, which is designed to hold air pressure when disconnected or when the trailer is not present.
Why the other options are wrong
- A. The leak is at the tractor's glad hand, indicating a tractor-side component issue.
- C. The question specifies the red glad hand, not the blue (service) glad hand.
- D. This is incorrect; the emergency line should seal itself to prevent air loss when disconnected.
Emergency Air Line Valve (Tractor)
A valve on the tractor that automatically seals the emergency (red) air line when it is disconnected from a trailer, preventing air loss from the tractor's air tanks.
- Seals the emergency line when uncoupled.
- Prevents air loss from tractor system.
- A leak indicates a faulty valve on the tractor.
Memory trick: Red leak when alone, the tractor's valve has flown.