BC Air Brake Practice · Question
When testing the tractor protection valve on a combination vehicle, what typically happens when the trailer air supply line is disconnected?
The tractor protection valve is designed to close and seal off the tractor's air system if there's a loss of air in the trailer system or if the trailer supply
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Question: When testing the tractor protection valve on a combination vehicle, what typically happens when the trailer air supply line is disconnected?
Answer options:
- The trailer service brakes apply automatically.
- The tractor's parking brake automatically applies. ✅ Air from the tractor's service reservoirs is prevented from escaping through the disconnected line.
- The low air warning buzzer will immediately cease.
Correct answer: Air from the tractor's service reservoirs is prevented from escaping through the disconnected line.
Explanation: The tractor protection valve is designed to close and seal off the tractor's air system if there's a loss of air in the trailer system or if the trailer supply line is accidentally disconnected. This prevents the tractor from losing its own service brake pressure.
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