A freight driver starts the tractor unit and conducts a stationary check of dashboard inst… — Commercial Driver's License (CDL) General Knowledge Exam

A freight driver starts the tractor unit and conducts a stationary check of dashboard instruments, cabin controls, and safety gear. Which observed condition indicates an equipment defect that must be repaired before operating the vehicle?

A
The cabin safety kit contains three red reflective warning triangles, spare electrical fuses, and a charged $10\text{ B:C}$ fire extinguisher.
B
The oil pressure gauge starts near zero at engine crank and stabilizes within normal operating limits within $4\text{ seconds}$ of running.
The power steering wheel exhibits $20^\circ$ of free play (approximately $3.5\text{ inches}$ of movement on a $20\text{-inch}$ wheel) before the linkage turns the tires.Answer
D
The dashboard voltmeter registers an electrical charging output of $14.1\text{ volts}$ while the engine idles.

Answer

Power steering wheel free play measuring

20^\circ

(approximately

3.5\text{ inches}

on a

20\text{-inch}

steering wheel) before tire engagement is an unsafe defect that must be corrected.

Federal commercial vehicle safety regulations specify that power steering play must not exceed

10^\circ

, which corresponds to approximately

2\text{ inches}

of free movement on a standard

20\text{-inch}

steering wheel. A steering wheel exhibiting

20^\circ

of movement (or

3.5\text{ inches}

) before turning the wheels indicates excessive mechanical slack that degrades vehicle control and constitutes a mandatory repair defect.

Step-by-Step Solution

Evaluate the mechanical steering play specification against federal inspection limits.

CDL regulations mandate that steering wheel free play on power steering systems must not exceed

10^\circ

, which equates to approximately

2\text{ inches}

of circumferential play on a standard

20\text{-inch}

steering wheel.

Steering play measuring

20^\circ

(or

3.5\text{ inches}

) exceeds legal limits and indicates worn steering linkages, universal joints, or a loose steering box.

Verify the operating parameters of the remaining in-cab indicators and emergency gear.

An oil pressure rise within

4\text{ seconds}

, a voltmeter output of

14.1\text{ volts}

, and an emergency kit with three red reflective triangles, fuses, and a

10\text{ B:C}

fire extinguisher all satisfy standard operational requirements.

Normal oil pressure builds within seconds of engine firing, charging voltage rests stably in the

13.5\text{ to }14.5\text{ volt}

range, and the emergency equipment list matches federal safety rules.

Key Concept

In-cab inspection standards for steering play tolerances, gauge stabilization, and mandatory emergency equipment.

Estimated Time:1m 0s

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