Instructions

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 three answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Idaho Commercial Driver’s License Manual l. 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 25

Passing Score 20

1. If the low air pressure warning signal comes on in a vehicle with air brakes, the driver should:

Test the brakes while driving, but continue driving if nothing seems wrong.

Immediately stop driving.

Drive with the hazard lights activated.

If the low air pressure warning signal comes on while you are operating a vehicle with air brakes, you should stop and safely park the vehicle as soon as possible. It is essential that you are able to stop safely while you still have some braking power remaining.

2. What does an air compressor do in an air brake system?

It pumps air into the air storage tanks.

It fills the tires.

It moves air to the back of the truck.

In an air brake system, the air compressor pumps air into the air storage tanks. The air compressor is controlled by the air compressor governor.

3. Alcohol evaporators are:

Illegal.

Used to add alcohol to braking systems to prevent items from freezing.

Only allowed on vehicles carrying hazardous materials.

Some air brake systems include an alcohol evaporator. The evaporator introduces alcohol into the braking system to prevent the formation of ice, which can cause damage.

4. The rods in S-cam brakes move the slack adjusters when air pressure is added to the brake chambers. This air pressure is added to the chambers when the driver:

Presses the brake pedal.

Uses the emergency brake.

Uses the trailer hand valve.

When pressing the brake pedal in a vehicle with S-cam brakes, air will enter the brake chambers. The added air pressure will push out the rods and move slack adjusters, twisting the brake camshafts.

5. You should test the low pressure warning signal by:

Turning on the engine and applying the trailer hand brake.

Rapidly pressing and releasing the brake pedal.

Removing wheel chocks and disengaging the parking brake.

It is essential that your low pressure warning light functions properly. After allowing the system to charge, you can test the warning signal by rapidly applying and releasing the brake pedal. This will release air from the braking system and the warning signal should come on when pressure drops to a dangerous level.