InspectionQuestion 40 of 60
When performing an air brake check on a combination vehicle, why do you test the tractor protection valve and trailer air supply valve?
a.To grease the valves
b.To change gear ratios
c.To check the paint
d.To confirm that if trailer air pressure drops too low, the valves close and protect the tractor's air supply
Explanation
The tractor protection valve and trailer air supply valve are tested to confirm they will close automatically when air pressure drops to a low level, typically between 20 and 45 psi. This protects the tractor's braking system if a trailer air line breaks. Confirming this function is a key part of the combination air brake check.
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- When inspecting the trailer's suspension system, what should you look for?
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- What should you check about the mounting of the fifth wheel skid plate and the trailer apron?
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