Vehicle Systems and Malfunctions Flashcards

What is the primary function of the air compressor governor in a vehicle's air brake system?

Answer: To control the cut-in and cut-out pressures of the air compressor.

The air compressor governor's specific job is to monitor the air pressure in the reservoirs and signal the compressor when to start pumping air (cut-in) and when to stop (cut-out) to maintain pressure within the correct operating range.

A driver is operating on a long, steep downgrade and notices they must press harder on the brake pedal to achieve the same stopping force. The pedal feels firm, but the truck is not slowing as it should. What is this dangerous condition called?

Answer: Brake fade

This scenario describes brake fade, which is a significant loss of stopping power that occurs when excessive heat from prolonged or hard braking reduces the friction between the brake shoes and drums.

Which of the following is a common symptom of a failing water pump in the engine's cooling system?

Answer: A grinding or whining noise from the front of the engine that changes with RPMs.

A failing water pump often has a worn bearing, which can produce a distinct grinding, whining, or squealing noise from the front of the engine that typically increases in pitch or volume as the engine speed increases.

While driving at night, a CMV driver notices the headlights are dimming and flickering, and the needle on the voltmeter is steadily dropping. These are primary indicators of a malfunction in which vehicle system?

Answer: The electrical system.

Dimming or flickering lights and a dropping voltmeter/ammeter are classic signs of a failing alternator, which is the component responsible for generating electricity and recharging the battery while the engine is running.

During a pre-trip inspection, a driver notices it is very difficult to shift into gear and hears a grinding noise, even with the clutch pedal fully depressed. This most likely indicates a problem with the:

Answer: Clutch

Difficulty shifting and grinding noises are classic symptoms of a clutch that is failing to disengage properly. This prevents a clean separation of the engine from the transmission, making gear changes difficult and noisy.

A driver is on the road when the low air pressure warning light and buzzer activate. What is the most critical and immediate action the driver must take?

Answer: Find a safe place to pull over and stop the vehicle as soon as possible.

The low air pressure warning indicates a critical loss of air, which will soon lead to the spring brakes applying automatically and a potential loss of braking control. The only safe and correct response is to stop the vehicle in a safe location immediately to diagnose the problem.