Automotive Servicing NC II flashcards

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

5S Workplace Organization

Seiri, Seiton, Seiso, Seiketsu, Shitsuke: sort, set in order, shine, standardize, sustain. The first three are physical cleanup actions; the last two maintain the result through standards and discipline.

Safety Data Sheet Purpose

The SDS is the authoritative document for a shop chemical. It lists hazards, first aid, firefighting measures, spill handling, PPE, and safe storage, and must be accessible to every technician using that chemical.

Lockout Tagout Verification

After isolating and locking an energy source, the technician attempts a start or tests for voltage to confirm zero energy. Each technician applies a personal lock so no one can re-energize the equipment.

Class C Fire Extinguisher

Used on energized electrical fires. Carbon dioxide and dry chemical are suitable because they do not conduct electricity. Water must never be used on an energized electrical fire.

Torque Formula

Torque equals force multiplied by lever arm length. A force of 100 newtons applied at 0.3 metres produces 30 newton-metres. Torque wrenches are accurate only within the middle of their marked scale.

Micrometer Reading Method

Read the sleeve in millimetres, then the thimble division that aligns with the sleeve line, multiplied by the least count. Add the two values. A 0.01 mm thimble adds hundredths to the sleeve reading.

Vernier Caliper Least Count

Least count equals one main-scale division divided by the number of vernier divisions. A 0.02 mm caliper has 50 vernier divisions spanning 49 main divisions, so each vernier line represents 0.02 mm.

Ohmmeter Measurement Rule

Resistance and continuity are measured with the circuit de-energized and the component isolated. Measuring ohms on a live circuit gives false readings and can damage the meter.

Feeler Gauge Clearance Test

The specified clearance is the thickest blade that slides in with light drag; the next larger blade must not enter. This method is used for valve clearances, spark plug gaps, and brake clearances.

Four-Stroke Cycle Order

Intake, compression, power, exhaust. The crankshaft completes two revolutions per cycle, so the camshaft turns at half crankshaft speed and the cam drives the valve events.

Wet Versus Dry Compression Test

A dry test records compression as-is. Adding oil to the cylinder raises a low reading if the rings are worn; if the reading stays low, the leak is at valves or the head gasket.

Compression Ratio Formula

Compression ratio equals swept volume plus clearance volume, divided by clearance volume. A larger ratio raises thermal efficiency but increases the octane or cetane requirement of the fuel.

Thermostat Stuck Open Effect

A thermostat stuck open lets coolant circulate continuously, so the engine warms slowly, heater output is low, and fuel consumption rises. A stuck-closed thermostat causes rapid overheating.

Coolant 50/50 Mixture Rule

A 50/50 mix of coolant and distilled water is typical. Excess coolant raises the freeze point and reduces heat transfer; insufficient coolant risks corrosion, scale, and freezing in cold weather.

Oil Viscosity Grade Meaning

The number before W describes cold pumping behaviour; the number after W is viscosity at 100 degrees Celsius. A higher second number suits hotter climates or worn engines with wider clearances.

Stoichiometric Air-Fuel Ratio

For gasoline, about 14.7 parts air to 1 part fuel by mass. Richer mixtures leave unburned fuel and raise carbon monoxide; leaner mixtures raise combustion temperature and nitrogen oxide emissions.

Fuel Pressure Leak-Down Test

After priming the rail, pressure is observed for about ten minutes. A rapid drop indicates a leaking injector, check valve, or pressure regulator; a slow drop may be normal for the design.

Diesel Injection Timing Effects

Advanced timing causes combustion knock and high nitrogen oxide emissions. Retarded timing causes white smoke, poor power, and higher fuel consumption because combustion continues after top dead centre.

Ohm's Law and Power

Voltage equals current times resistance. Power equals voltage times current. A 12-volt circuit drawing 5 amperes has 2.4 ohms resistance and dissipates 60 watts of heat.

Voltage Drop Test Rule

Measure voltage across a conductor or connection while the circuit carries its normal load. More than about 0.5 volts on a 12-volt power or ground path indicates excessive resistance.

Battery State of Charge

A rested 12-volt battery reads about 12.6 volts at full charge, 12.4 volts at roughly 75 percent, and 12.0 volts at about 25 percent. Each cell contributes about 2.1 volts.

Alternator Output Specification

With the engine running and electrical loads applied, charging voltage at the battery is typically 13.8 to 14.5 volts. A reading below about 13.2 volts suggests a charging fault.

AC Ripple Diode Test

Set the meter to AC volts across the battery with the engine running. Excessive AC ripple indicates one or more failed alternator diodes, which also causes dim lights and noise.

Pascal's Law in Brakes

Pressure applied to a confined fluid is transmitted equally in all directions. Force equals pressure times piston area, so a larger wheel-cylinder bore produces greater braking force.

DOT 3 Versus DOT 5 Fluid

DOT 3 and DOT 4 are glycol-based and absorb moisture, lowering their boiling point over time. DOT 5 is silicone-based and must never be mixed with glycol fluid.

Brake Bleeding Order

Begin at the wheel farthest from the master cylinder and work toward the nearest, keeping the reservoir topped up. Air trapped in the system produces a spongy pedal.

Spongy Versus Sinking Pedal

A spongy pedal indicates air in the hydraulic system. A pedal that sinks slowly under steady pressure indicates internal bypass in the master cylinder. A hard pedal suggests a booster fault.

Camber Definition and Wear

Camber is the inward or outward tilt of the wheel viewed from the front. Positive camber wears the outer tread edge; negative camber wears the inner edge.

Toe Wear Pattern

Incorrect toe produces feathered wear, with tread edges scuffed in opposite directions across the tire. Toe is the last alignment angle set, after camber and caster.

Thrust Angle Effect

The thrust angle is the bisector of rear toe. A non-zero thrust angle causes dog-tracking and an off-centre steering wheel, and it must be corrected before front alignment.

Clutch Slip Versus Drag

Slip shows engine speed rising without matching vehicle speed, often under load. Drag shows difficult gear engagement and creeping with the pedal depressed, caused by insufficient release travel.

Gear Ratio Formula

Gear ratio equals driven gear teeth divided by driving gear teeth. Overall ratio is the gearbox ratio multiplied by the final drive ratio, which determines engine speed at a given road speed.