Heavy truck brakes test 2023

When a truck has no air pressure in its tanks, which warning devices are activated when the ignition key is turned on? - ANSWER-A buzzer, a dash gauge and a red light What legislation mandates every required standard of a highway truck air brake system? - ANSWER-FMVSS 121 If a truck is FMVSS 121 compliant, which of the following air reservoirs must be incorporated into the air brake circuit? - ANSWER-Supply, primary and secondary tanks In a truck air brake system which sub circuit is primarily responsible for actuating front axle service brakes when the system is functioning normally? - ANSWER-Secondary circuit When a FMVSS 121 compliant tractor trailer combination is moving down the highway at a speed of 50 mph, which circuit must be charged with air? - ANSWER-Hold off circuit What best describes the functions of a tractor protection valve? - ANSWER-Pressure protects the tractor air supply in the event of loss of pressure in a trailer Routes trailer supply air and service application signal to the trailer pneumatic circuits Blocks service signal air to the trailer until trailer air supply is activated If you have yo make an adjustment to air system cut off pressure where should the adjustment be made? - ANSWER-The governor How is the relay section of an FMVSS 121 compliant duel circuit foot valve activated when the air brake is functioning properly? - ANSWER-Pneumatically What is the function of a quick release gladhand when used? - ANSWER-Speeds service brake release timing What best accounts for brake feel in an air brake system? - ANSWER-Resistance of application pressure versus for pressure What is the potential energy of an air brake system? - ANSWER-Compressed air When a tractor spring brake assembly is charged with air on both its service and hold off chambers what results is known as? - ANSWER-Compounding What is true about hold off pressure in current truck and trailer air brake systems? - ANSWER-Its regulated at 90 psi.