Alabama CDL — Air Brakes Practice Test 9

1.What is the purpose of an alcohol evaporator in an air brake system?

It cools the compressor during hard brakingIt lowers the risk of ice forming in the brake valvesIt replaces the need to drain the tanksIt boosts the pressure the compressor can build

2.What is 'brake lag' in an air brake system?

The time the compressor needs to refill the tanksThe delay before the air reaches and works the brakesThe wait for the spring brakes to releaseThe pause between draining two air tanks

3.When is it best NOT to set the parking brakes?

When the brakes are very hot, or very wet in freezing weatherWhenever the vehicle is parked on level groundAny time the trailer is loadedWhen the air tanks are fully charged

4.How is the parking brake checked as part of the final air brake test?

Release it on a downgrade and count how far the vehicle rollsSet it with the vehicle stopped and tug against it gently in a low gearApply it at highway speed and time how long the stop takesWatch the application gauge for one minute with the key off

5.When checking a slack adjuster on an s-cam brake by hand, how much movement suggests it probably needs adjustment?

More than about one inch of movementAny movement at all, even a fraction of an inchMore than about six inches of movementOnly if it does not move whatsoever

6.What inspection method should be used to check a vehicle equipped with air brakes?

A quick glance at the dash gauges onlyA brake test performed only at highway speedAn inspection limited to the trailer connectionsThe basic seven-step inspection procedure

7.At roughly what tank pressure does the governor stop the compressor from pumping more air (the cut-out point)?

About 55 psiAbout 80 psiAbout 150 psiAbout 125 psi

8.What does the application pressure gauge show?

The reserve air remaining in the tanksWhether the parking brakes are engagedHow much air pressure is being applied to the brakesThe compressor's cut-in and cut-out settings

9.If the low air pressure warning comes on while driving, why is it safer to stop while air still remains in the tanks?

The compressor cannot restart once the warning soundsThe brake lights stop working below the warning levelThe parking brake knob will jam if pressure is lostYou can still use the foot brakes for a controlled stop while air lasts

10.On a tractor or straight truck, spring brakes will come fully on when air pressure drops into roughly what range?

About 80 to 100 psiAbout 100 to 125 psiAbout 20 to 45 psiAbout 125 to 150 psi