A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R - S - T - U - V - W - X - Y - Z
This Glossary is not yet complete and is a 'work-in-progress'. The rest is coming soon.
| A | Ampere, usually called an amp, the unit for measuring electrical current |
| AATS | Ambient air temperature sensor |
| AB | Air bleed |
| ABCM | Antilock brake control module |
| ABCV | Air bleed control valve |
| ABDC | After bottom dead center |
| Abnormal wear | Excessive wear on a drive or driven member. Possible causes include abrasive materials in the road/driving surface, improper tensioning or misalignment |
| Abnormal wear patterns | Uneven wear of the tire tread. Can indicate incorrect wheel alignment, and the need for balancing and/or rotation |
| Abrasion resistance | The treatment of a wire's insulation to reduce wear |
| Abrasive | A hard substance used for the removal of material |
| Abrasive finishing | The removal of scale or surface contaminants using abrasives |
| ABRS | Air bag restraint system |
| ABS | Antilock Braking System |
| A/C | Air conditioning |
| AC | Alternating current |
| AC adapter | A power supply that plugs into an AC power outlet to provide low voltage AC or DC power |
| AC Current | An electrical current that flows in one direction in the circuit then reverses it's flow direction |
| ACCS | Air Conditioning Cycling Clutch Switch |
| Acceleration sensor | A sensor that provides information about the rate of acceleration or deceleration |
| Acceleration squat | When the rear of a vehicle presses down on the rear springs during acceleration |
| Accelerator pedal position sensor | A sensor that transmits the position of the accelerator pedal as an electrical signal to the CPU |
| Acetone | A powerful ketone-type lacquer solvent |
| Acetylene | A highly flammable gas used for metal cutting, welding, and brazing |
| Ackerman principle | The geometric principle used to provide toe-out on turns |
| Ackerman steering | Otherwise known as Ackerman principle |
| ACM | Air Control Module. A component of the fuel control system that monitors intake air volume and meters fuel accordingly |
| ACOV | Air cut off valve |
| ACR3 | Air Conditioning and Refrigeration Refrigerant Recovery, Reclaim, and Recycle system |
| ACR | Air Conditioning Relay |
| Active plate material | The sponge lead in a battery that is spread over the negative-plate grid, or, the lead peroxide that is spread over the positive-plate grid |
| Active restraint | A safety restraint system that is attached or connected to the person using it, e.g. a seatbelt or safety harness |
| Actuator | Translates hydraulic pressure into mechanical energy |
| ACV | Air-control valve. Used to route air from the pump to either the exhaust manifold or to the catalytic converter |
| A/D | Analog to Digital |
| Adaptive suspension system | A suspension system that changes ride characteristics by continuously altering shock damping and ride height |
| A/D Converter | Analogue to Digital Converter. A circuit that translates an analogue signal into digital |
| Additive | A substance when combined with lubricating grease or oil, the cooling system, or gasoline, improves or gives it extra performance enhancing properties, for e.g. rust inhibitors, the increase or decrease of boiling point or freezing point, the improvement of gasoline quality |
| Adhesion | The quality in oil that allows it to bond to bearings and other metal surfaces The ability of a tire to remain in contact with the driving surface |
| Adjustable shock absorber | A shock absorber that can be adjusted for specific operating conditions |
| Adjustable strut | A strut that can be adjusted to vary the strut orifice opening |
| Adjusting cam | Eccentric bolts that are used to automatically or manually adjust the brake shoe-to-drum clearance. Positioned in the backing plate of drum brakes, the cam positions the shoe(s) closer to the drum |
| AERA | Automotive Engine Rebuilders Association |
| Aerobic sealer | Used to hold parts together - a silicone rubber sealing compound that requires oxygen for curing |
| Aerodynamic drag | The resistance of air against a moving object, also known as air drag and air resistance |
| A/F | Air Fuel Ratio, also see below |
| AFR | Air Fuel Ratio. The chemically correct air-fuel ratio necessary to achieve complete combustion of the fuel (stoichiometric ratio) |
| AFS | Air Fuel Sensor, also see below |
| * A/F sensor | |
| Afterburner | An engine exhaust manifold that burns any HC and CO remaining in the exhaust gas |
| Aftermarket | The sale of parts and equipment after the manufacture of a vehicle typically by dealers, garages, and other retailers operating independently from the vehicle manufacturers |
| AFV | Alternative Fuel Vehicle |
| Airbag | A flexible membrane or envelope, inflatable to contain air or some other gas. Air bags are most commonly used for cushioning, in particular after very rapid inflation in the case of a collision |
| Airbag system | Airbags are supplemental restraints, and operate best when the occupant is also using a seat belt. Airbags supplement the safety belt/seatbelt by reducing the chance that the occupant's head and upper body will strike some part of the vehicle's interior. They also help reduce the risk of serious injury by distributing crash forces more evenly across the occupant's body |
| Air brake | Air-operated braking systems are used on heavy vehicles. Compressed air, operating on large-diameter diaphragms, provides the large forces at the brake assembly that are needed |
| Air cleaner | An air cleaner filters air that passes through it to stop harmful particles reaching the engine |
| Air compressor | One of two engine driven mechanisms (for in-line engines or v-type engines) for supplying high pressure air to truck brake systems, or, an engine driven mechanism for supplying air for air tools, lifts, and paint spraying equipment etc. |
| Air conditioner | The function of the air-conditioning system is to reduce the temperature inside the passenger compartment to a level that ensures passenger comfort, it achieves this by removing excess heat and transferring it to the outside of the vehicle |
| Air cooled | When heat has been removed from the engine by circulating air across the cylinder block and heads |
| Air cooling | The removal of heat from the engine by directing airflow over the extended metal fins on the cylinder head and the block to maintain a stable vehicle operating temperature |
| Air filter | A filter that removes contaminants from from the air passing through it |
| Air foil | The inverted wing of a race car designed to increase downward aerodynamic force and, with it, vehicle traction |
| Air inlet valve | A moveable door in the plenum blower assembly that permits the selection of outside air or inside air for both heating and cooling systems |
| Air intake and exhaust system | The system of parts used to move air through the engine and expel the exhaust, includes air cleaner, muffler, tail pipe |
| Air jack | A tool that uses compressed air to lift a vehicle, on some high-performance race cars this is built into the chassis enabling the car to be raised completely off the ground instantly |
| Air line | A hose, pipe or other similar tubing through which air passes |
| Air lock | A pocket of air that blocks the normal flow of liquid in a system |
| Air pollution | The release of contaminants (carbon monoxide (CO), oxides of nitrogen (NOx), sulfur, hydrocarbons, and particulate matter (PM) or soot) into the atmosphere, the main sources being vehicles, industry, power plants, and smaller equipment such as lawn mowers |
| Air shock | A manually adjustable air spring that is incorporated into each rear shock absorber. The air spring consists of a flexible rubber cylinder which seals the outside of the upper and lower halves of the shock absorber. Also known as load-adjustable shock absorbers |
| Air shock absorber | A standard hydraulic type shock absorber, providing normal dampening action, but when a heavy load is placed on the rear of the vehicle, the rubber air cylinder can be pressurized to assist the suspension springs. Also known as load-adjustable shock absorbers |
| Air spring | A manually adjustable air spring that is incorporated into each rear shock absorber. The air spring consists of a flexible rubber cylinder which seals the outside of the upper and lower halves of the shock absorber. |
| Air spring suspension | A single or multi-axle suspension relying on air springs and weight distribution of axles |
| Air temperature sensor | A device that’s sensitive to engine temperature sends readings to a temperature gauge or a warning lamp. To give an accurate reading this sensor must always be immersed in liquid |
| Air conditioner muffler | A device to reduce compressor pumping sounds, located in the compressor discharge line |
| Air cooled engine | An engine that is cooled by the passage of air with the use of cooling fins. Their design makes the exposed surface area as large as possible, which allows more heat energy to radiate away, and be carried off in convection currents in the air, or in the case of a slow moving vehicle a fan with shrouds and ducts to direct air to the cylinders |
| Air injection system | The supply of fresh air to the exhaust system to assist catalytic converter to convert unacceptable exhaust pollutants, such as carbon monoxide, certain hydrocarbons and oxides of nitrogen into less dangerous substances |
| Air injector system | Engine emission control system that injects fresh air at each exhaust point to mix with the exhaust gases to reduce hydrocarbon and carbon monoxide exhaust emissions |
| Air-over-hydraulic brakes | Brakes utilizing a hydraulic system assisted by an air pressure system |
| Airborne | Contaminants light enough to be suspended in the air stream flowing through the engine |
| Airflow meter | Used to measure the volume of air entering the engine on fuel injection systems |
| Alkali | A chemical base (the opposite of an acid), can be used as fuel cell electrolytes |
| ALDL | Assembly Line Diagnostic Link |
| Alkaline fuel cell | A type of hydrogen/oxygen fuel cell in which the electrolyte is concentrated potassium hydroxide and hydroxide ions are transported from the cathode to the anode |
| All-season tire | Tires with a tread designed to improve handling and traction on snow or in icy conditions |
| All-terrain vehicle | A small, lightweight, four-wheeled vehicle with high flotation tires designed primarily for off-road use |
| All-wheel drive | A vehicle with a drivetrain with a center differential having all four wheels under power at all times |
| Alligator clip | A long-nosed, spring-loaded metal clip with meshing teeth used to make temporary electrical connections |
| Alloy | A metal containing additions of other elements (metallic or nonmetallic) to enhance specific properties such as corrosion resistance and strength |
| Alphanumeric | All letters in the alphabet and the numbers 0 through to 9 |
| Alternative refrigerant | An ozone friendly HFC-134a that is used to replace ozone depleting CFC-12 |
| Alternator | Universally used in automotive applications, it converts mechanical energy into electrical energy, by electro-magnetic induction |
| Altitude | The height above sea level is important to automotive emissions control because the higher the altitude, the fewer oxygen molecules in the air adversely effects compression and air/fuel ratios |
| Aluminum | A light weight versatile engineering and construction material that has a high resistance to corrosion and is an excellent conductor of heat and electricity. Some of it's alloys have strengths greater than steel |
| Aluminum cylinder block | An engine block cast of aluminum or aluminum alloy, usually with cast iron sleeves installed as cylinder bores |
| Ambient | All around and encompassing |
| Ambient air temperature | The air that surrounds an object |
| Ambient sensor | A thermistor is used in automatic temperature control units to sense ambient temperature, it senses the outside air temperature and uses the information as an input to the system |
| Ambient temperature | The temperature of the air surrounding a vehicle |
| Ambient temperature sensor | A sensor that measures the outside air temperature as it enters the evaporator |
| AMM | Air Mass Meter |
| Ammeter | An ammeter is a measuring instrument used to measure the flow of electric current in a circuit. Electric currents are measured in amperes. Commonly misspelled or mispronounced as "ampmeter" |
| AMP | Ampere |
| AMP/hour | Amperes per hour. A standard measure for a rate of current flow |
| Amperage | An amount of current, expressed as amperes |
| Ampere | Usually called an amp, the unit for measuring electrical current |
| Ampere Turns | The unit of measurement for electrical magnetic field strength |
| Analog instrument | An instrument that displays measurements with a needle on a dial |
| Analog signal | An electrical signal that varies in amplitude within a given parameter |
| Anchor | A mounting point on a vehicle for a stressed, non-structural component such as a seat or seat belt |
| Anchor end | The end of a brake shoe that is attached to a fixed point on the backing plate |
| Anchor pin | The steel pin attached to the backing plate of drum brakes. Return springs are attached to the anchor pin and to the brake shoes to hold the shoes against the anchor pin in a non-applied position. In an applied position it prevents the shoes from rotating with the drums |
| Anion | A negative ion. Alkali, molten carbonate and solid oxide fuel cells are 'anion-mobile' cells |
| Anode | The positively charged electrode in an electrolytic cell toward which current flows |
| Anodize | An electrochemical process that coats and hardens the surface of aluminum |
| ANSI | American National Standards Institute. A privately funded organization that promotes uniform standards in areas such as measurements |
| Antenna | A conductive metallic structure used for radiating or receiving electromagnetic signals, such as those for radio transmissions and television signals |
| Anti-backfire valve | A valve that is used in the air-injection system to prevent backfiring in the exhaust system during deceleration |
| Anti-foam agent | An additive that reduces foaming caused by the churning action of the crankshaft in the engine oil |
| Anti-fouler | Also known as a spark plug non-fouler. If an engine is "burning oil", the excess oil leaking into the combustion chamber tends to foul the plug tip and inhibit the spark, on older engines with severe oil burning problems the adapter can be installed between the plug and the head to reduce the protrusion of the plug which will reduce buildup (fouling) and increase performance |
| Anti-icers | An alcohol such as ethanol, methanol, or isopropyl added to gasoline to prevent freezing |
| Anti-knock index | Also known as Research Octane Number (RON), Pump Octane Number (PON), or (R+M)/2. It is a measure of how resistant the fuel is to premature detonation (knocking). It is measured relative to a mixture of 2,2,4-trimethylpentane, so an 87-octane gasoline has the same knock resistance as a mixture of 87% isooctane and 13% n-heptane. |
| Anti-lock brake | A system on motor vehicles which prevents the wheels from locking while braking. It consists of a brake pedal, a master cylinder, wheel speed sensors, the electronic control unit or ECU, and the hydraulic control unit, also called a hydraulic modulator |
| Anti-lock brake control module | Also known as CAB (Controller Anti-lock Brake). The electronic unit constantly monitors the rotation speed of each wheel. When it senses that one or more wheel is rotating slower than the others (a condition that will bring it to lock) it moves the valves to decrease the pressure on the braking circuit, effectively reducing the braking force on that wheel and causing a characteristic pulsing feel through the brake pedal |
| Anti-oxidant | A chemical that prevents the oxidation (loss of an electron by a molecule, atom, or ion; loss of hydrogen, or gain of oxygen) |
| Anti-roll bar | Also known as a sway bar, anti-sway bar, or stabilizer bar (not to be confused with a roll bar). A steel torsion bar running across the car as part of the front and, less frequently, rear suspension layout and used to reduce body roll during cornering |
| Anti-rust additive | A substance added to coolant to retard rust formation inside the cooling system |
| Anti-skid control | A blanket term for systems such as Anti-lock brakes |
| * Anti-smog device | |
| Anti-sway bar | (United States) Also known as an Anti-roll bar, sway bar, or stabilizer bar. A steel torsion bar running across the car as part of the front and, less frequently, rear suspension layout and used to reduce body roll during cornering |
| Anti-theft system | Security system; either an alarm system, or an additional locking device (e.g. steering wheel lock), or an electric circuit immobilizing the car by disconnecting the starter and/or ignition |
| AOC | Abnormal operating conditions |
| API | American Petroleum Institute. A petroleum-industry lobbying and public information group |
| * Arc braze welding | |
| Arcing | Sparking and discharge at the contact breaker points in the distributor, a cause of premature wear of the points; the spark that occurs in an electrical circuit in an air gap, such as a spark plug |
| Arc welding | A welding process widely used for do-it-yourself repairs in which the welding current is generated by a transformer, and the circuit is closed when the electrode held in the welding rod holder touches the metal surface; the electrode burns off as the rod holder is moved along |
| Arming | Activating the vehicles alarm system |
| Aromatic | A type of solvent based on benzene ring molecules |
| Articulated vehicle | A vehicle made in two separate sections, with a joint or coupling between them; especially of commercial vehicles consisting of a tractor or towing unit and a trailer, having a swiveling coupling giving better maneuverability |
| AS | Airflow sensor. Measures airflow in an electronic fuel injection system, processed with other sensory data by the electronic control module to calibrate the air/fuel mixture |
| Asbestos | A fibrous material that is heat resistant and nonburning, once used in brake linings, gaskets, and clutch facings, it is no longer used due to health hazards |
| ASE | National Institute for Automotive Service Excellence |
| Aspect ratio | The ratio between the height and the width (e.g. of a tire - also known as tire profile) |
| Assembly | The process or result of putting together a number of components |
| Asymmetrical cam | A camshaft that has different profiles for the intake and exhaust lobes |
| Asymmetrical rear-leafing spring | A spring on which the rear axle is not located in its center |
| Asynchronous Fuel Timing | Fuel injector firing which is not in direct relationship to the ignition reference pulses |
| Atmospheric pressure | The pressure exerted by the atmosphere at the earth's surface. At sea level it is 14.6959 psia or 101.325 kilopascals (kPa) |
| Atmospheric pressure sensor | A device designed to send an electrical signal to the central processing unit relative to the current atmospheric pressure |
| ATDC | After Top Dead Sensor. The position of a piston as it begins it's intake or power stroke |
| A/T | Automatic Transmission |
| Atom | The smallest division of an element still retaining all of the original properties of the element |
| Atomization | The production of a fine spray from a liquid by a device, e.g. paint in a paint gun |
| Attenuation | The reduction of noise or emissions |
| Attenuator | An attenuator is a device that reduces the amplitude of a signal without appreciably distorting its waveform |
| Attrition | Process of wearing out by friction, as with pellets in catalytic converters (attrition severely reduces the useful service life of pellet-type converters) |
| ATV | All-Terrain Vehicle |
| Automatic adjuster | A drum-brake mechanism that adjusts the lining clearance as wear occurs. It is commonly actuated on reverse stops or when the parking brake is set |
| Automatic choke | A device in the carburetor intake which positions the choke valve automatically in accordance with engine temperature or time |
| Automatic door locks | A passive system used to lock all doors when the required conditions are met, for e.g. when the vehicle is placed in drive, the ignition switch is in RUN, and all doors are properly shut |
| Automatic headlight dimming | Also known as automatic beam control. A device on automobiles which used a photoresistor to automatically adjust the headlight beams from "high beam" to "low beam". Although intended to only occur in the path of an oncoming vehicle, the headlights tended to erratically flicker between low- and high-beams in response to minor fluctuations of light, such as street lamps |
| Automatic level control | Also known as leveling system. A suspension system that automatically adjusts front and rear ride heights to compensate for changes in axle loads; this can either be achieved by adding air shock absorbers to a conventional suspension system, or by incorporating the system in a sophisticated pneumatic or hydropneumatic suspension system |
| Automatic on/off with time delay | An automatic headlight control system; headlights turn on automatically when ambient light decreases to a predetermined level, and headlights remain on for a length of time after the vehicle has been turned off |
| * Automatic tensioning | |
| Automatic Traction Control | Also known as Traction Control System, Anti-Spin Regulation (ASR), ASR Traction Control System, and ASC. The control or prevention of wheelspin under power by means of electronic sensing and in conjunction with anti-lock breaking |
| Automatic transmission (AT, A/T) | Transmission which changes the gear ratio without assistance from the driver and without interruption of power flow, the changes being governed by factors such as engine load and vehicle road speed. The driver usually has a manual override |
| * Automatic transmission cooler | |
| Automatic transmission fluid (ATF) | A special oil used in automatic transmissions |
| Automotive | of, relating to, or concerned with self-propelled vehicles or machines. (Merriam-Webster definition) |
| Automotive air conditioning | System of filtering air and keeping it at a desirable temperature and humidity level; air is cooled, cleaned and dehumidified before the air enters, or re-enters, the passenger compartment |
| Automotive air pollution | Exhaust gas, fuel and crankcase fumes released into the atmosphere |
| Automotive cooling system | System for keeping the temperature of an engine down to a desirable level, usually by the circulation of water with additives; comprised of a radiator, hoses to connect it to the engine, water passages in the cylinder head and block, and a pump |
| * Auxiliary air valve | A device that allows air to bypass a closed throttle during star-up and warm-up |
| * Auxiliary drum parking brake | The incorporation of a secondary parking-brake drum inside the rear rotor on some four-wheel drive disc-brake systems |
| Axle housing | Also known as axle casing. The external, basically tubular housing containing the differential and half-shafts and with bearings at either end for the hubs |
| Axle load | Also known as axle weight. That part of the weight of a vehicle resting on the wheels of an axle |
| Axle shaft | The short shaft connecting the differential and the drive shaft on each side in an independent suspension layout; The drive shaft, or the half-shaft in a rigid axle |
| AWD | All wheel drive. A more common term for 'full-time four wheel drive'. The engine drives all four wheels of the vehicle at all times. |
| AWG | American Wire Gauge. A standard for the measurement of the size of wire, the higher the gauge number the smaller the wire |
