NAVTTC Auto Electrician key terms

A safety procedure in which the energy source of a vehicle or machine is isolated, locked, and marked with a tag so it cannot be re-energised while someone works on it.

Items worn by a technician to reduce injury risk, such as safety glasses, insulated gloves, coveralls, and safety footwear, selected according to the task and its hazards.

The immediate response to electrolyte contact: flush skin or eyes with plenty of clean water for at least 15 minutes and seek medical help; neutralising agents are not used on skin.

The risk created by explosive hydrogen gas released from lead-acid batteries during charging; sparks, flames, and smoking must be kept away and the area ventilated.

Precautions for hybrid and electric vehicle circuits above roughly 60 V DC, including isolation, approved insulated tools, verified de-energisation, and never assuming a cable is dead.

A precision measuring instrument with a calibrated screw spindle, used to measure small thicknesses such as shaft diameters, commutator wear, or brush length to within hundredths of a millimetre.

A measuring tool with sliding jaws and a graduated scale that reads outside, inside, and depth dimensions, commonly used for checking pulley, rotor, and housing sizes.

A set of thin metal blades of marked thickness used to check small gaps, such as spark plug gaps, valve clearances, or armature-to-pole air gaps.

A wrench that indicates or limits applied turning force so fasteners are tightened to a specified value, preventing stripped threads, distortion, and loose electrical terminals.

A hand tool that compresses a terminal or connector onto a conductor to form a permanent mechanical and electrical joint; the correct die and terminal size must be matched.

Joining conductors by melting a filler alloy onto cleaned, heated metal; in vehicle wiring it must produce a shiny, smooth joint protected by heat-shrink sleeving.

A polymer sleeve that shrinks when heated to insulate and seal a splice or terminal, giving strain relief and protection against moisture and abrasion.

A drawing that shows electrical components and the conductors connecting them, with wire colours, connector numbers, and pin identifiers used to trace circuits during diagnosis.

The relationship stating that current equals voltage divided by resistance (I = V/R); it allows a technician to predict how a circuit will behave when voltage or resistance changes.

A circuit in which components are connected one after another so the same current flows through all of them and the total resistance is the sum of the individual resistances.

A circuit in which components share the same voltage across them while current divides between branches; total resistance is lower than the smallest branch resistance.

A loaded measurement of the difference in voltage between two points in a live circuit; excessive drop reveals high resistance at connections, cables, or ground points.

A resistance check performed with the circuit de-energised to confirm that a conductor or switch provides a complete, low-resistance path between two points.

A test instrument combining voltmeter, ohmmeter, and often ammeter functions, used to measure electrical values and to check diodes, continuity, and circuit conditions.

A diagnostic instrument that displays voltage against time, allowing analysis of fast-changing signals such as ignition pulses, injector commands, and charging ripple.

The return path to the battery negative terminal through the vehicle body or engine; a poor ground causes dim lights, slow cranking, and false sensor readings.

The maximum current a fuse is designed to carry continuously before its element melts; replacing a fuse with a higher rating risks cable overheating and fire.

An electromagnetically operated switch that lets a small control current switch a larger load current, commonly used for horns, lamps, fuel pumps, and starter circuits.

An unintended low-resistance path that bypasses the load, causing excessive current flow, blown fuses, overheating, and possible fire.

A break in a circuit path that stops current flow, resulting in a non-working component with no voltage available beyond the break.

A rechargeable battery using lead plates and sulphuric acid electrolyte, providing the high current needed for cranking and acting as a stabiliser for the vehicle electrical system.

The sulphuric acid and water solution inside a lead-acid battery that conducts ions between the plates during charge and discharge; its level and specific gravity indicate condition.

A tool that measures the specific gravity of battery electrolyte, indicating state of charge and helping identify a weak or failed cell in a serviceable battery.

The current a battery can deliver for 30 seconds at -18 degrees Celsius while keeping terminal voltage above a specified level; it indicates starting capability in cold conditions.

A small current drawn from the battery when the ignition is off, caused by a faulty component or module; excessive drain flattens the battery overnight.

Charging a battery at a raised current or voltage to restore it quickly; it must be controlled to avoid overheating, gassing, and plate damage.

A high-torque electric motor that turns the engine flywheel through a pinion during cranking, drawing very high current from the battery for short periods.

An electromagnetic switch that both engages the starter pinion and closes the heavy-current contact supplying the starter motor, controlled by the ignition switch circuit.

A belt-driven generator that produces alternating current, rectifies it to direct current, and charges the battery while supplying the vehicle's electrical loads when the engine runs.

A set of six diodes inside the alternator that converts the alternating current produced by the stator into direct current for the battery and electrical system.

A control device, usually built into the alternator, that limits charging voltage to a safe range so the battery is charged without overcharging or boiling electrolyte.

A transformer that steps battery voltage up to the very high voltage needed to jump the spark plug gap, producing a spark at the correct moment.

The air space between the centre and ground electrodes of a spark plug; it must match the manufacturer's specification for reliable sparking and efficient combustion.

The moment, relative to piston position, at which the spark occurs; incorrect timing causes hard starting, poor power, overheating, or engine damage.

The correct alignment of a headlamp beam, set so the road ahead is lit without dazzling oncoming drivers; it is checked with a beam setter and adjusted at the lamp mountings.

A measurement made with an insulation tester to confirm that a conductor's insulation is intact and not leaking current, important on high-voltage and motor circuits.