Air Brakes

This endorsement is required for driving a vehicle with air brakes. To receive this endorsement, applicants must pass a written test. The test consists of 25 multiple choice.. Read More

This endorsement is required for driving a vehicle with air brakes. To receive this endorsement, applicants must pass a written test. The test consists of 25 multiple choice questions. Each question has two, three or four answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the South Carolina Commercial Driver License Manual. Questions come from the chapter covering: Air Brakes. The Air Brakes endorsement may be used with the Class A, B or C CDL.

Number of Question
Passing Score

7. If the low pressure warning light comes on while you are driving:

Explanation
When driving a vehicle with air brakes, if the low air pressure warning light comes on, it is important for you to stop and safely park your vehicle as soon as possible. There may be a leak in the system. Controlled braking will remain possible only as long as there is enough air left in the tanks.

8. ____ make up the emergency brake system.

Explanation
In an air brake system, there are three different braking systems: a service brake system, a parking brake system, and an emergency brake system. The emergency brake system uses parts of both the parking and service brake systems.

9. What kind of force must emergency brakes use?

Explanation
Because air pressure can eventually leak away, the emergency brakes in an air brake system must be held on by mechanical force.

10. Air brakes are:

Explanation
As long as the brakes are properly maintained, using air brakes is a safe and effective method of stopping large, heavy vehicles.

11. During an inspection, slack adjusters on S-cam brakes should not move more than:

Explanation
Check each slack adjuster after parking on level ground, setting wheel chocks, and disengaging the parking brake. Pull the slack adjusters to make sure they do not move more than about one inch from where the push rod is attached. If they move more than one inch, they may be out of adjustment and will need to be fixed.

12. What is a wig wag?

Explanation
A wig wag is a type of low air pressure warning device in an air brake system. It drops a mechanical arm into the driver's view when the air pressure in the tanks falls below 60 psi.
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