What is the purpose of the trailer air supply control?
Answer: A
To control the tractor protection valve
The trailer air supply control controls the tractor protection valve while supplying the trailer with air pressure.
All choices
- ATo control the tractor protection valve
- BTo control air compressor governor cut-in and cut-out
- CThe control brake relay valves for the tractor brakes
Why the other answers are wrong
B. To control air compressor governor cut-in and cut-out
The trailer air supply control does not regulate the air compressor governor.
C. The control brake relay valves for the tractor brakes
It does not control the brake relay valves for the tractor brakes.
CDL Combination Vehicles Test Info
Questions on Exam
20
Passing Score
80%
Time Limit
Typically 30 minutes; varies by testing location
The Combination Vehicles test content is federally standardized, so this question applies in every state. Age limits, fees, and testing procedures do vary — check your state's CDL requirements.
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More CDL Combination Vehicles Practice Questions
- There are two things that a driver can do to prevent a rollover. They are: (1) keep the cargo as close to the ground as possible and (2):
- Off-tracking or cheating causes which of these to follow the wider path while making a turn?
- When driving behind another vehicle, under good conditions, you should allow at least one second between your vehicle and the vehicle ahead for each ____ feet of your vehicle length.
- Which part of the kingpin should the locking jaw close around?
- Where should the tractor be when you inspect the landing gear after uncoupling the trailer?