CDL

Question 1

Air Compressor

Answer 1

pumps air into the storage tanks

Question 2

Air compressor governor

Answer 2

controls when the compressor will pump air into the storage tanks

Question 3

air storage tanks

Answer 3

holds the compressed air used in the braking system

Question 4

air tank drains

Answer 4

drain built up water or oil in the bottom of the tanks

Question 5

alcohol evaporator

Answer 5

puts alcohol into the air system to reduce the risk of ice

Question 6

safety valve

Answer 6

automatically opens at a set PSI, usually 150. to prevent too much pressure in the air brake system

Question 7

brake pedal

Answer 7

engages the air brakes when pressed

Question 8

foundation brakes

Answer 8

the brakes used at each wheel. They are most commonly S-cam brakes but can also be wedged brakes or disc brakes

Question 9

supply pressure gauges

Answer 9

connected to the air tanks and indicate the pressure in each tank

Question 10

application pressure gauge

Answer 10

displays how much pressure is being applied to the brakes.

Question 11

low air pressure warning

Answer 11

alerts when the air brake pressure falls below a safe amount (usually 60 PSI)

Question 12

stop light switch

Answer 12

turns on the brake lights when applying the brakes, alerting anyone behind that the vehicle is slowing

Question 13

front brake limiting valve

Answer 13

only on the vehicles made before 1975. When set to “slippery” it cuts the standard air pressure to the front brakes in half.

Question 14

spring brakes

Answer 14

used for the emergency and parking brake systems. Powerful springs are help back by air pressure and when that air pressure is released that springs allow for braking. Spring brakes are not installed on steering axles. Steering axles are not part of the emergency braking systems. steering axles are part of the service brake system only.

Question 15

parking brake control

Answer 15

usually a yellow diamond shape, push-pull knob. On older vehicles, the parking brake may be controlled by a lever

Question 16

trailer protection valves

Answer 16

usually a red, octagon-shaped, push-pull control knob

Question 17

controlled braking

Answer 17

used in emergency stops. applying the brakes as hard as possible without locking the wheels

Question 18

stab braking

Answer 18

used in emergencies, pressing on the brake pedal until the brakes lock up, releasing the brakes, and then as soon as the wheels begin rolling again, pressing the pedal back down as hard as you can.