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
H
H.A.S.W.A.: Health And Safety at Work Act 1974.(UK)
Half Shafts: Shafts by which power is transmitted from final drive to driven wheels in an enclosed axle.
Hall Generator: An electronic pulse generator using the Hall effect of a semiconductor to provide information to the ignition amplifier or ECU on engine position and speed.
Hall IC: Integrated circuit as part of a Hall sensor.
Hall Sensor: An electronic pulse generator using the Hall effect of a semiconductor to provide information to the ignition amplifier or ECU on engine position and speed. Also used for sensing road speed etc.
Halogen: A description of a series of gases such as argon.
Handbrake: Hand operated parking brake usually with a mechanical linkage. Also forms the reserve or emergency brake on many vehicles.
Handbrake Cable: A cable that operates the brakes when a lever is pulled.
Handbrake Linkage: Cables or rods used to operate the parking/handbrake.
Harmonic Balancer: Rotating or oscillating engine balance shaft.
Harness: The collection of vehicle cables wound together with an insulation tape. Also known as a 'wiring loom'.
Hazardous: Risky. Potential to harm people or property.
HC: (1) Hydrocarbon. (2) High compression.
Head Gasket: Seal between cylinder block and cylinder head.
Head-up Display: Projection of instruments onto the windscreen so that the road and the instruments can be seen at the same time by the driver.
Header Tank: The expansion tank at the top of a coolant radiator, which can be part of the radiator or a separate tank.
Headlamp: Vehicle lighting that provides illumination of the road for the driver. Usually consists of switched main and dipped beams.
Headway Sensor: A device usually fitted in the front grill of a vehicle that in conjunction with a transmitter senses distance in front of the vehicle. Often part of an active cruise control system.
Heat: A form of energy in all materials that can be used to do work.
Heat Exchanger: A device for transferring heat from one system or place to another.
Heat Sink: A plate to which electronic components are attached to dissipate heat.
Heater Matrix: Small radiator used to exchange heat from the coolant to the vehicle cabin.
HEGO: Heated Exhaust Gas Oxygen Sensor. Also EGO Exhaust Gas Oxygen Sensor, EOS Exhaust Oxygen Sensor and Lambda sensor. Provides information to the fuel system ECU on the oxygen content in the exhaust gas.
HEI: High Energy Ignition. A distributor ignition system using electronic control of the coil secondary output.
Helical Gear: A gear with teeth cut at an angle.
Helical Rotor: A turbine or compressor in a turbocharger often has vanes that are helically shaped.
Helical Spring: Metal spring used in vehicle suspension. Also known as a coil spring.
Heptane: A fuel used in research tests as a comparison when determining the octane rating of fuels. Octane value of zero.
Hertz: The number of oscillations per unit of time. The SI unit for frequency is the Hertz which equals one oscillation per second.
Hex: Short for hexagonal.
Hide Mallet: Soft hammer made of hide (leather). Plastic types are also used.
High Lift Cam: A special cam profile used on performance engines to increase the opening size of a valve.
High Tension: The term used for the high voltage in the secondary circuit of the ignition system.
HLG: Hall generator. A sensor using a Hall effect to provide signals to an ECU.
Hoist: To lift something or a term used to describe a vehicle lift or ramp.
Hold-in Winding: A winding in a starter motor solenoid that holds the switch contacts together and the drive pinion in mesh during engine starting.
Hone: A light grinding process applied to cylinder bores in preparation for the fitting of new pistons.:
Hooke's
Horizontally Opposed: An engine configuration where cylinder pairs are fitted on opposite sides of the crankshaft. Sometimes referred to as 'Boxer' engines.
Horsepower: A measure of power equivalent to 0.746 Kilowatts. Defined by a rate of doing work of 33,000 foot pounds per minute (550 foot pounds per second).
HOS HO2S: Heated Oxygen Sensor.
Hose Clamp: Simple ring type clamp to seal a hose onto a pipe.
Hot Idle Compensator: A device to change idle or mixture settings when an engine is hot.
Hot Stamping: A machine forging process using a series of dies to create the completed shape.
Hot Wire: A small thin wire that is heated an placed in an air flow. The change in temperature is used to determine the rate of air flow.
HT Cables: High tension leads (high voltage) used to supply the spark.
HT Leads: High tension leads (high voltage) used to supply the spark.
Hub: Centre of a wheel or gear or similar.
Hub Nut: Main nut that secures a wheel hub.
Hunting: Uneven running of an engine, usually when the mixture is over rich.
HVAC: Heating, ventilation and air conditioning.
Hydraulic: A system for transmitting and modifying force by the use of a liquid. Consists of a pump, control devices, hydraulic lines and slave cylinders.
Hydraulic Brake: Brake actuated only by hydraulic pressure.
Hydraulic Clutch: A clutch, operated by fluid pressure.
Hydraulic Hoses: Hoses that carry fluid under high pressure.
Hydraulic Lifters: Hydraulic cam followers in the valve opening mechanism.
Hydraulic Pedestal: Self adjusting support for a finger tappet in the valve opening mechanism.
Hydraulic Pressure: Pressure applied by a fluid.
Hydraulic Tappets: Self-adjusting cam followers in valve opening mechanism.
Hydraulic Valves: Valves used to control pressure or flow of a hydraulic fluid.
Hydrocarbon (HC): Chemical compound which contains only, or principally, Carbon and Hydrogen. The principal constituent of liquid fossil fuels.
Hydrocarbon Emissions: Fuel vapours released into the atmosphere from a vehicle exhaust or fuel tank.
Hydrometer: Instrument used for measuring specific gravity/relative density of a liquid (coolant, battery electrolyte).
Hydro-pneumatic Suspension: A suspension system using a liquid to transfer suspension movements to pneumatic (gas) springs.
Hygroscopic: Absorbs moisture from atmosphere.
Hypoid Gearing: Bevel gear with the axes of the driving and driven shafts at right angles, but not in the same plane, giving some sliding action between teeth. Widely used in rear axle final drives.