Automotive Servicing NC I flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Hierarchy of control

Ranking of hazard controls from most to least effective: elimination, substitution, engineering controls, administrative controls, and personal protective equipment. PPE is last because it protects only the wearer and depends on correct use.

Near miss

An unplanned event that did not cause injury or damage but had the potential to do so. It is recorded and investigated because it reveals a hazard before a real incident occurs.

Job hazard analysis

A method that divides a task into sequential steps, identifies the hazards of each step, and assigns controls before work begins. It is reviewed when the task, tools, or environment change.

Manual handling limit

A practical guide for lifting: keep the load close, bend the knees, avoid twisting, and seek help or a mechanical aid for loads above about 25 kilograms or awkward shapes.

Fire extinguisher classes

Extinguishers are matched to fuel: A for solid combustibles, B for flammable liquids, C for flammable gases, D for metals, and K for cooking oils. Electrical fires require a non-conductive agent.

Vernier caliper least count

The smallest value the instrument can read, equal to the main scale division divided by the number of vernier divisions. A 0.02 mm caliper has 50 vernier divisions on a 1 mm main scale.

Micrometer reading

Total reading equals the sleeve reading plus the thimble reading. On a metric micrometer the spindle advances 0.5 mm per thimble revolution, and the thimble is divided into 50 parts.

Torque wrench use

Set the specified torque, apply force smoothly to the handle, and stop when the wrench signals. It tightens fasteners only, is never used to loosen, and is recalibrated periodically.

Feeler gauge principle

Thin blades of known thickness measure a gap. The correct clearance is the blade that fits with slight drag, while the next larger blade must not enter the gap.

Dial indicator runout

A dial indicator on a magnetic base measures shaft or disc runout. The plunger is set perpendicular to the surface and the shaft is rotated to read total indicated runout.

Wrench pull rule

Pull a wrench toward you rather than pushing, so that if the fastener slips the hand moves away from the work. Use the correct size to prevent rounded corners.

Cold tyre pressure

Tyre pressure is set when the tyre is at ambient temperature, before driving. Pressure rises with heat, so checking a hot tyre gives a falsely high reading.

Tread wear limit

The legal minimum tread depth is 1.6 mm, measured in the main circumferential grooves. Uneven wear across the tread indicates incorrect inflation, alignment, or suspension faults.

Battery open-circuit voltage

A fully charged 12 V lead-acid battery reads about 12.6 V at rest. About 12.4 V indicates partial discharge, and a load test confirms whether it can still crank the engine.

Brake fluid hygroscopy

Brake fluid absorbs moisture from the air, which lowers its boiling point. Dark colour and moisture content above roughly three percent mean the fluid should be replaced.

Severe duty service interval

Frequent short trips, heavy loads, dusty conditions, and stop-start traffic shorten maintenance intervals. The manufacturer schedule applies by distance or time, whichever comes first.

Four-stroke cycle

The sequence of intake, compression, power, and exhaust strokes. Each cylinder completes one power stroke per two crankshaft revolutions, and the camshaft turns at half crankshaft speed.

Wet and dry compression test

A dry test measures cranking compression. If a cylinder is low, a small amount of oil is added and the test repeated; a rise points to worn rings, no change points to valves or gasket.

Valve clearance adjustment

With the engine cold, a feeler gauge measures the gap between cam and follower. The gap is set to specification by adjusting the rocker screw or replacing shims.

Interference engine

An engine in which valve and piston paths overlap. A broken or mistimed timing belt causes contact and bends valves, so the belt is replaced at the specified interval.

Engine mount inspection

Mounts are checked for cracked or separated rubber and loose fasteners. Excessive movement appears as clunking during acceleration or deceleration and as engine vibration in the cabin.

Ohm's law

Voltage equals current multiplied by resistance, written V = I x R. Power in watts equals voltage multiplied by current. These relationships are used to diagnose circuits and size fuses.

Voltage drop test

A voltmeter is connected across a circuit while it operates under load. A drop above about 0.5 V on a main cable indicates unwanted resistance at a connection or cable.

Series and parallel circuits

In series, current is the same throughout and voltage divides. In parallel, voltage is the same across branches and current divides. Most vehicle circuits are parallel.

Alternator charging voltage

With the engine running, battery terminal voltage is typically 13.5 to 14.5 V. Excessive AC ripple measured at the battery indicates a failed rectifier diode.

Fuse rating rule

A fuse is replaced only with the same rating. A higher rating allows excess current and risks fire, while a blown fuse signals a short or overload that must be found first.

Brake pedal free play

The small travel before the pushrod contacts the master cylinder piston. Too much free play gives a low pedal; too little prevents full release and causes brake drag and overheating.

Brake bleeding order

Air is removed from the hydraulic system by opening the bleeder screws in sequence, usually starting at the wheel farthest from the master cylinder. The reservoir is kept topped up.

Toe-in and toe-out

Toe is the difference in distance between the front and rear of the wheels. Toe-in means the wheels point inward, toe-out means outward; incorrect toe causes feathered tyre wear.

Steering free play

Movement of the steering wheel rim before the road wheels respond, normally about 25 to 50 mm. Excess free play indicates wear in the steering box, linkages, or tie-rod ends.

Clutch slip symptom

Engine speed rises without a matching increase in vehicle speed, especially under load. Causes include a worn friction disc, weak pressure plate, oil contamination, or insufficient release free play.

CV joint clicking

A rhythmic clicking from the front during full-lock turns indicates a worn outer constant-velocity joint. Vibration under acceleration instead suggests the inner joint or shaft balance.

Final drive ratio

The number of ring gear teeth divided by the number of pinion teeth. Changing the ratio alters acceleration and cruising engine speed, and affects speedometer accuracy.