Chapter 33—Heavy-Duty Truck Trailers
65. What is the function of a trailer pressure protection valve?
maintain reservoir pressure
maintain pressure in the service line
maintain pressure in the supply line
maintain pressure in the brake chamber
66. A trailer with two air tanks suffers a total loss of pressure in one reservoir. Which of the following should prevent
immediate dynamiting of the trailer brakes?
service brake relay valve
spring brake control valve
pressure protection valve
hold-off quick release valve
67. If a trailer is equipped with a service brake priority air system and all its reservoirs are empty, which of the following
must occur before the trailer brakes can be released?
all service chambers must be charged
air tanks must be charged to 60 psi before the hold-off circuit is charged
the service signal circuit must be activated
spring brakes over one axle must be caged
68. What is the FMVSS-121 minimum required stopping distance for a tractor-trailer semi rig built after 2010?
69. When system air pressure is routed into the trailer hold-off circuit, the parking brakes are:
70. What is the reason for modulating hold-off pressure in the spring brake circuit?
faster park/emergency brake application
modulated park/emergency brake application
more aggressive service braking
modulated service braking
71. When setting a rivet using a pneumatic rivet gun, what tool should be used on the shank side of the rivet gun to form
the bucked head?
72. Technician A says that the bucked side of a rivet is usually countersunk. Technician B says that any bucked head