Definitions for Automotive Terms A-F
AC
Alternating current.
AC Generator
Device that produces alternating current; an alternator.
Airflow Sensor
Device to monitor flow of outside air into engine.
Alternator
An AC generator.
Ampere
Measurement of the amount of current.
Amplifier
Electronic circuit that uses a small current to control a much larger current.
Amplify
To increase in strength or volume.
Analog
A signal that can vary continuously in value.
Armature
Rotating support for multiple windings in a motor.
Backup Light Switch
An electrical switch that completes a circuit to the back up lights whenever the reverse gear if engaged.
Basic Circuit Problem
One caused by something in the circuit itself that increases or decreases an electrical value.
Battery Activation
To fill with electrolyte then charging a dry battery.
Battery Cables
Heavy gauged wires connected to the battery. Typically two are used. One, connects the battery to the starter (positive) and the second from the battery to a grounding point on the vehicle.
Battery Charge Condition
The state of its plates and electrolyte.
Battery Charger
Device for restoring battery to a proper electrical charge.
Battery Drain Test
A method of checking for unusual current draw with ignition key off.
Battery Leakage Test
Check to determine if current is discharging across top of battery case.
Battery Load Test
A test for battery capacity, made under full electrical load.
Battery Terminal Test
A test for good contact between cables and terminals.
Battery Voltage
For batteries used in modern cars, 12.6V; older cars, 6.3V.
Battery Voltage Test
Check of battery charge with a voltmeter.
bhp
Abbreviation for brake horsepower, a measurement of usable horsepower of an engine.
Block Diagram
A simple drawing, using rectangles and lines, that shows how sensors, computers, and actuators are interconnected.
Brushes
Sliding electrical contacts that ride on the slip rings of a generator.
BTU
British thermal units; the units used to measure heat transfer.
Bus
A pathway for data inside a computer.
Case
The outer protective shell of a battery, or any other component or device.
Cell
An electrical energy storage device, consisting of negative and positive plates immersed in a conductive fluid (electrolyte).
Cell Voltage Test
Check of individual battery cells for correct charge.
CFM
Cubic feet of air per minute.
Charge Indicators
Dash-mounted warning light, voltmeter, or ammeter used to show charging system status. Also the visual symbol (often a green dot) that shows state of charge in a battery.
Charging
Current flowing into a battery from an alternator.
Charging System
One that uses an alternator to replace the electrical energy drawn from the battery during starting.
Charging System Output Test
A measurement of current and voltage output of the charging system under load.
Charging Voltage
Alternator output that is higher than battery voltage (usually 1 3V- I 5V).
Circuit
Closed path through which electric current flows.
Circuit Board
A base upon which computer circuits are printed and components are mounted.
Circuit Breaker
Device that interrupts current if a circuit is overloaded or a short occurs. Unlike a fuse, it can be reset.
Circuit Resistance Tests
Measurements of resistance in the insulated and ground circuits of the system.
Closed Loop
Control system that is constantly changing, based on inputs from sensors.
CO
Abbreviation for carbon monoxide, a toxic byproduct of partial burning of fuel.
C02 Readings
Used to evaluate the air-fuel ratio of the engine; measured in percent by volume.
Coil Oscillations
Voltage fluctuations shown on an oscilloscope after the spark plug stops firing.
Cold Start Injector
Valve that supplies extra fuel for cold starts.
Commutator
Sliding electrical connection between motor windings and brushes.
Commutator End Frame
The end housing on a motor, holding the brushes, brush springs, and shaft bushing.
Computer
Electronic device used to control many systems of modern vehicles.
Computer Amplifier
Device that strengthens signals inside the computer.
Computer Analyzer
A more complex testing instrument than a scanner.
Computer-Coil Ignition
A distributor less ignition system using sensors, a control unit, and multiple ignition coils.
Computer Controlled Carburetor
One that calculates and sets air-fuel ratio based on input from sensors.
Computer Harness Connector
Plug at the end of a wiring harness, with one prong for each wire.
Computerized Emission Control System
A computer controlled system that uses sensors, a catalytic converter, and fuel injection to minimize emissions of harmful substances.
Computer Memory
Storage area where data is held electronically.
Computer Terminal Values
Voltage and resistance values at the ECU connector, read by a digital VOM
Condenser
An electrical component in contact point distributors that prevents arcing as points open and close.
Conductor
A material that permits easy flow of electrons.
Contact Point Regulator
An older type of voltage regulator that has largely been replaced by the electronic type.
Contact Points
In older distributors, the spring-loaded electrical "make/break" switch contacts.
Continuous Injection
Fuel injection that is constant.
Crank Position Sensor
Similar to a distributor pickup coil, the sensor is activated by the teeth on a pulse ring in a crankshaft triggered ignition system.
Crankshaft Triggered Ignition
System that places trigger wheel and pickup coil on the crankshaft damper at the front of the engine.
Crimping Pliers
Special tool used to mechanically fasten connectors to wires.
Current
Electricity flowing (from positive to negative) in a circuit.
Cylinder Balance Test
Oscilloscope test that measures the power output from each of the engines cylinders.
Cycle
One complete reversal of current from positive to negative.
DC (direct current)
Electric current that only flows in one direction.
Digital Pyrometer
An electronic device for making accurate temperature measurements.
Digital Signal
One made up of strictly on-off (or high-low) pulses.
Dimmer Switch
A switch that controls high-beam and low-beam headlamp functions.
Diode
Electronic device that allows current flow in only one direction.
Diode Test
Check for open or shorted conditions in a diode, using an ohmmeter or special test equipment.
Discharging
Flowing out (describing current movement related to a battery).
Display Output
Actuator that provides readable characters on a small screen or liquid crystal display.
Dry Charged
Battery that is filled with electrolyte just before being installed in a vehicle.
Dwell
The amount of time distributor points remain closed between openings.
Dwell Meter
One that measures point setting in degrees of distributor rotation.
Dwell Section
Section of oscilloscope pattern used to identify problems in the distributor or electronic control unit.
Dwell Signal
Electronic signal output by carburetor that can be read on a special meter for troubleshooting.
Dwell Variation
Change in meter readings indicating distributor wear.
Dynamometers
Instrument used to measure power output and performance of an engine.
ECA
Electronic control assembly; another name for an automotive computer.
ECM
Electronic control module; another name for an automotive computer.
ECU
Electronic control unit; another name for an automotive computer.
EFI
Electronic fuel injection
EGR Valve
Air Gas Re-circulation Valve. A valve allowing exhaust gases to re-enter the intake manifold to be burned again, reducing cylinder temperature and some types of toxic emissions.
Electric Engine Fan
One operated by an electric motor, under control of a thermostatic switch.
Electric Fuel Pump
An electrical device that uses a rotary motion to move fuel.
Electrolyte
Liquid that surrounds the plates of a battery and allows a free flow of electrons.
Electronic Advance
A system that uses sensor input and the vehicle's computer to control spark timing.
Electronic Coil Module
Grouping of ignition coils and the control unit needed to operate them.
Electronic Control Unit
Another term for a computer used in a vehicle.
Electronic Ignition System
One that uses an electronic control circuit and distributor pickup coil points and condensers to break the field of the ignition coil, sending voltage to the spark plug.
Electronic Ignition Tester
Instrument used to identify source of ignition problems.
Electronic Regulator
Solid-state regulator separate from the alternator.
Engine Sensors
Devices that monitor temperatures, fluid levels, and other engine conditions for computer input.
Fast Idle Solenoid
Device that holds throttle plates open when engine is operating, but lets them almost close when engine is shut off.
FHP
Frictional horsepower.
Field Windings
Stationary windings in a motor that creates a magnetic field to keep the armature rotating.
Firing Line
The tall spike shown on an oscilloscope, representing the voltage needed to make the spark jump the plug gap.
Firing Order
Sequence in which the spark plugs fire in cylinders.
Flux
Paste used in soldering to assist the flow of molten solder.
FM
Frequency modulation (type of radio broadcasting).
Four-Gas Analyzer
Measuring instrument that provides the reading of oxygen and carbon dioxide, as well as HC and CO, levels in exhaust.
Fuel Accumulator
Diaphragm that dampens pressure pulses in a fuel injection system.
Fuel Distributor
Hydraulically operated valve used to control fuel flow in a continuous injector system.
Fuel Evaporization System
A combination of technologies and components that prevents fuel vapors from entering the atmosphere.
Fuel Injector
Fuel valve controlled by a coil or solenoid.
Fuel Pressure Regulator
System that controls pressure of fuel entering injector valves.
Fuel Pump Pressure
The pressure of a fuel pump's output.
Fuel Pump Vacuum
The amount of "pull" exerted on fuel by the pump.
Fuel Pump Volume
The amount of fuel discharged by a pump in a measured period.
Fuel Rail
Tubing that connects several injectors to the main fuel line.
Fuel Return System
One that keeps cool fuel circulating to prevent vapor lock.
Fuse
Device that interrupts current if a circuit is overloaded or a short occurs.
Definitions for Automotive Terms G-L
Gasoline Injection
System that uses computers, sensors and electrically operated injectors to meter fuel into an engine.
Gas Turbine
Engine that uses burning and expanding fuel vapor to spin fan-type blades
Hard to Start Problem
Usually caused by a partial system failure, such as a choke refusing to open.
HC
Abbreviation for hydrocarbons (unburned fuel).
HC ReadingsThe parts-per-million measuring of hydrocarbon emission.
HesitationCondition in which engine does not accelerate immediately when gas pedal is pressed.
Gross HP
Horsepower developed with only basic accessories in use.
Growler
Testing device used to check armatures for shorts.
Hall Effect
A type of pickup used with many electronic ignition systems.
Halogen Headlamp
One with a small, high-intensity halogen lamp inside a conventional scaled housing.
Hard Failure
One that is always present (not intermittent), such as a disconnected wire.
Horsepower
Measure of an engine's ability to perform work.
Hot Idle Compensator
Component that prevents stalling when engine temperature is high.
Hydraulic Actuator
Solenoid-operated valve and electric pump mechanism.
Hydrometer
Tool used to test for specific gravity indicating the condition of a batteries electrolyte and its ability to charge/hold a charge.
Idle Air Control Valve
Solenoid operated valve in a Till system that regulates idle speed.
Idle Mixture Screw
Adjusting device that meters fuel into the air horn.
Ignition Coil
Device used to produce the high voltage needed for ignition spark.
Ignition Computer
ECM that controls ignition timing, based on sensor input.
Ignition Distributor
Component that directs coil voltage to each spark plug at the appropriate time.
Ignition Lag
The time required for diesel fuel to vaporize, heat up, and begin to burn.
Ignition Spark Switch
Used on some manual transmissions, this switch permits distributor vacuum advance in high gear.
Ignition System
Components that produce a spark to ignite the air-fuel mixture in the engine.
Ignition Timing
How early or late the spark plug fires in relation to the piston position.
IHPIndicated horsepower.
Improper Injector Spray Pattern
One that is restricted due to foreign matter in the injector.
Initial Ignition Timing
Timing set with ignition idling.
Injector
A spring-loaded valve that meters fuel into the pre-combustion chamber of a diesel engine.
Injector Leakage
Dripping or spraying of fuel when the injector nozzle is closed.
Injector Opening Pressure
Amount of pressure needed to open the injector nozzle.
Injector Output Volume
The amount of fuel output over a specific time period.
Injector Spray Pattern
Shape of the spray produced by an injector.
Inlet Air Temperature Sensor
The device that checks temperature of air entering the engine.
Insulated Current Resistance Test
Check of all parts between the battery positive and the starting motor for excess resistance.
Insulator
A material that resists the flow of electrons.
Integral Regulator
A regulator that is mounted in or on an alternator
Integrated Circuit
A tiny "chip" of silicon containing complete electronic circuits.
Intermittent ProblemOne that occurs only under some conditions.
Jumper Cables
Electrical cables used to start a car with a dead battery.
Jumper Wire
A wire used to make a temporary electrical connections when testing electrical circuits.
KAM
Keep-alive memory.
Kick-Down Valve
Component that causes automatic transmission to shift down into a lower gear during fast acceleration.
Knock
Engine noise caused by detonation.
Knock Sensor
Engine sensor that detects detonation in the engine.
kV
Kilovolt (1000 volts).
Leaking Injector
One that allows extra fuel to drip out, causing a richer mixture.
Lean Air-Fuel Ratio
An air-fuel mixture that contains more air than a stoichiometric mixture.
Load or Acceleration Test
Oscilloscope reading that measures the firing voltages of the spark plugs when the engine is accelerating rapidly.
LPG
Liquefied petroleum gas, an alternate fuel.
Definitions for Automotive Terms M-R
Magnetic Field
Field of force generated around an electrical conductor.
Magnetic Sensor
One that uses part movement (such as rotation) and induced current to produce a signal for a computer.
Mag-Tach
A magnetically triggered tachometer usable on both gasoline and diesel engine.
Main Body
Central portion of the carburetor, forming the air horn and fuel bowl.
Main Jet
Fuel inlet metering device for normal-speed engine operation.
Maintenance-Free Battery
One without removable filler caps that does not require periodic filling with water.
Manifold Pressure Sensor
Measures pressure inside the intake manifold. Also called MAP sensor.
Mechanical Choke Unloader
A linkage that opens the choke plate whenever the throttle swings fully open.
Metering Rod
Stepped rod that moves in and out of main jets to alter fuel flow.
MillisecondFraction (1000th) of a second.
Missing
Failure of one or more cylinders to fire.
Mixture Control Solenoid
Electromechanical; device that opens and closes air and fuel passages in carburetor.
Modulated Injection
Injection of fuel intermittently, without reference to intake valve timing.
Multi-Point
Fuel injection system that sprays fuel into port for each cylinder.
Multi-Meter
An electrical test device that can be used to measure voltage, current, or resistance.
Net hp
Maximum horsepower developed with all accessories in use.
Neutral Safety Switch
Switch that prevents engaging the starter when the vehicle is in gear.
Noise Suppressor
Capacitors that absorb voltage fluctuations in a car's electrical system, reducing radio noise.
Normal Aspiration
System that provides air to the engine at normal atmospheric pressure.
No Start Problem
Engine turns over but refuses to fire.
NOx
Abbreviation for oxides of nitrogen, pollutants resulting from high combustion temperatures.
O2 Readings
Oxygen must be present for proper catalytic converter functioning. Analyzers measure it in percentage by volume.
Octane Number
Indicators of the antiknock value of a gasoline.
Ohm
Unit of electrical resistance.
Ohm's Law
A simple formula for computing unknown electrical values when two values are known.
Oil Pressure Switch
Safety device that shuts off the fuel pump if engine oil pressure drops.
One-Wire Circuit
One that uses the vehicle frame as a return wire to the power source.
Open Circuit
Electrical circuit with a gap or break in continuity so that current cannot flow.
Open Injector Coil
A broken wire in the solenoid coil is preventing operation.
Open Loop
Control system using preset values in the computer to operate engine.
Operating Parameter
An acceptable maximum or minimum electrical value.
OscilloscopeInstrument that displays line patterns that relate voltages to time.
Output
The signal sent by a computer (for example, to an actuator) as a result of processing inputs it has received.
Oxygen Sensor
Device that monitors oxygen content in engine exhaust to correct air-fuel ratio.
Parade Pattern
Oscilloscope pattern that shows traces for each cylinder from left to right across the screen.
Passive Sensor
One that changes an externally produced signal, but does not generate its own voltage.
Pickup Coil
Component that sends pulses to the control unit of an electronic ignition system as a result of trigger wheel rotation.
Pickup Coil Air Gap
Space between the pickup coil and trigger wheel tooth.
Ping
A mild knock (light tapping noise) caused by pre-ignition of fuel.
Pinpoint Tests
Specific tests of individual components of a vehicle, using the electronic scanner.
Pintle
An inward-opening diesel injector nozzle, with fuel flow controlled by a pintle (needle tip).
Plate
A grid, covered with porous lead, that will store electrical energy.
Plug Gap
Distance between the center and side electrodes on a spark plug.
Plug Heat Range
Numeric indicator of how hot a spark the plug will develop.
Plug Reach
Length of the threaded portion of a spark plug.
POA
Pilot operated absolute valve.
Polarity
Direction current is moving though a circuit.
Pole Piece
Magnetic component of motor that keeps the armature rotating.
Port Injection
Another name for multi-point injection.
Potentiometer Sensor
One that changes resistance in response to external change (such as part movement).
Power
The rate or speed at which work is done.
Power Valve
A device that performs the same function as a metering rod.
Pre-Ignition
Ignition of fuel before it is fully compressed in the cylinder.
Pressure Chamber
Area around the needle valve of an injector where pressure builds up to open valve.
Pressure Regulator
A limiting device in an automatic transmission, regulating maximum hydraulic oil pressure.
Pressure Relief Valve
Spring-loaded bypass that operates when pressure reaches a preset point.
Primary
In a carburetor, the components that operate under normal driving conditions.
Primary Circuit
In an ignition system, all components operating on battery (low) voltage.
Primary Pattern
Pattern of low-voltage (ignition primary) changes, as shown on an oscilloscope.
Primary Wire
Small insulated conductor that carries battery or alternator voltage.
Printed Circuit
One that consists of conductors that are flat metallic strips applied to an insulating board base. Other components are mounted on the board, as well.
Probe Tools
Used to view or retrieve items in hard-to-reach areas. Mirrors and magnetic pickups are examples.
PROM
Programmable read-only memory.
Pulse Air System
System that produces the same results as an air injection system, but uses natural pressure pulses in the exhaust system to provide airflow.
Pulse Ring
A trigger wheel placed on the crankshaft damper in a crankshaft triggered ignition system.
Pulse Width
An indication of how long an injector is energized and kept open.
Purge Line
Line connecting the charcoal canister and engine intake manifold.
RAM
Random access memory.
Raster Pattern
Oscilloscope pattern that shows the traces for the cylinders stacked vertically, bottom to top.
Reading Oxygen Sensor Tip
A visual inspection of tip color, which indicates engine condition.
Reading Spark Plugs
Determining cause of a problem by examining condition of the spark plug.
Rectified
Term used to describe AC current that has been changed to DC.
Reference Voltage
A known voltage (usually 0.5 V) fed to passive sensors by a computer. Changes in sensor resistance can then be read by the computer.
Refractometer
Test instrument used to measure antifreeze protection.
Regulator Bypass Test
Test that connects full battery voltage to the alternator field, leaving the regulator out of the circuit.
Regulator Voltage Test
Test of the charging system under low output, low load conditions.
Relay
Electrically operated switch.
Relay Actuator
One that uses a smaller current flow to operate a switch controlling a larger current flow.
Resistance
Opposition to current flow.
Resistance Plug Wire
Special type of spark plug wire that eliminates most radio interference.
Resistor - Electric device that limits the flow of current (ohms)
Reverse Polarity
Accidental backward connection of primary wires.
Rich Fuel/Air Ratio
A fuel/air mixture that contains more fuel than needed..
Rollover Valve
Safety feature that prevents gasoline from leaking out tank vent if car rolls over.
ROM
Read-only memory.
Rosin Core Solder
Soft metal compound used to join electrical wires. The rosin is a non-corrosive flux to aid bonding.
Rotor Current Test
Method used to check alternator windings for an internal short.
Rotor Winding Open
An open (broken) winding in an alternator rotor.
Rotor Winding Short
short-to-ground fault in an alternator rotor.
Definitions for Automotive Terms S-Z
Schrader Valve
A spring-loaded valve, similar to a tire valve, used in fuel injection systems.
Secondary
In a carburetor, the components that operate under high engine output conditions.
Secondary Circuit
In an ignition system, all components operating on coil (high) voltage.
Secondary Pattern
Pattern of high-voltage (ignition secondary) changes, as shown on an oscilloscope.
Secondary Wire
Wire used in a vehicle ignition system. It carries high voltage from coil to spark plugs.
Secondary Wire Resistance
A type of test performed to check condition of a spark plug wire or coil wire.
Sensor
Device that monitors and reports a condition (such as engine temperature) to the vehicle computer.
Sensor Rotor
A toothed wheel that operates at the same rpm as the vehicle wheel.
Separator
An insulating material placed between plates of a battery.
Service Valves
Points at which pressures in a fuel injection system can be checked.
Servo Motor
One that can be stopped in exact positions (degrees of rotation).
Servo Motor Actuator
A small DC motor that can turn or move parts.
Short Circuit
Excess current flow that occurs when a conductor touches ground.
Shorted Condenser
One with a direct electrical connection to ground.
Shorted Injector Coil
A short-circuited solenoid coil is preventing injector operation.
Simple Circuit
One consisting of a power source, a load, and conductors.
Single-Point
Injection system with fuel sprayed from a single location into the intake manifold.
Sintered Bronze Filter
A porous metal fuel filter.
Slow Charger
One that feeds a small current into the battery over a long period of time.
Smooth DC
Direct current without "ripples" or "spikes" due to fluctuating voltages.
Solder
Soft, wire-like metal of tin and lead used to bind wires together.
Soft Failure
One that is intermittent, such as the make/break connection from a loose terminal.
Soldering Gun
Tool that applies heat to joined wires so that solder can be melted into the joint.
Solenoid Actuator
One with a moving metal core that is actuated by an induced magnetic field.
Spark Knock
Noise caused by spark plug firing too early.
Spark Line
Oscilloscope line showing voltage needed to maintain an arc across the spark plug gap.
Spark Plug
Devices that emit an electrical arc at the tip to ignite the air-fuel mixture in an engine cylinder.
Spark Test
Check of the spark intensity (brightness and length of arc).
Spark Tester
Device used to cheek operation of ignition system.
Starter Current Draw Test
Starting test that establishes the number of amps used by the starting system.
Starter Ground Circuit Resistance Test
Check of all parts between the battery negative and the starting motor ground for excess resistance.
Starter Mounted Solenoid
One with a plunger that moves to engage the pinion gear with the flywheel gear.
Starter Relay
Device that uses a small current flow from the ignition switch to control a larger current flow to the starter solenoid.
Starter Shims
Thin metal pieces used to adjust the space between the pinion gear and the flywheel gear.
Starter Solenoid
A high current relay that energizes the starter motor.
Starting Headlight Test
Starting test conducted with headlights turned on to provide a load on the battery.
Starting System
Electric motor and other components used to rotate the engine until it starts.
Stator
The stationary magnetic field in a generator. Also component of torque converter that improves oil circulation and thus, torque.
Stator Support
A stationary tube surrounding the input shaft of a torque converter and supporting the stator.
Stator Test
Ohmmeter check for open or shorted windings in the stator.
Stethoscope
A medical device, also used by auto technicians to better hear internal engine noises.
Stoichiometric Fuel Mixture
A perfect (chemically correct) air-fuel mixture.
Strap
Connector between cells of a battery.
Stratified Charge
A combustion chamber design that first ignites the air-fuel mixture in a small chamber connected to the main chamber.
STY
Suction throttling valve.
Superimposed Pattern
Oscilloscope pattern in which the traces for all cylinders are placed one on top of the other.
Surging
Condition in which engine power fluctuates up and down.
Switching Sensor
One that opens or closes a switch in response to a change in condition.
Systematic Approach
Combining knowledge and a logical process of elimination to solve a problem.
Tach-Dwell
Combined meter that measures engine rpm and degrees of breaker cam rotation for distributor point adjustment.
Taxable hp
General rating of engine size.
TBI
Throttle body
(single-point) fuel injection.
TDC
Top Dead Center
When the engine cylinder piston achieves its highest position within the cylinder.
Telescoping Gauge
Spring-loaded device for measuring inside dimensions (such as a cylinder bore).
Temperature Gauge Tester
Electronic device for testing accuracy of engine temperature gauge.
Terminals
The positive and negative posts or threaded connectors on a battery.
Test Light
Device that will light up to show the presence of voltage (electrical potential).
Thermo-Time Switch
Control circuit that energizes cold start injector when temperature is low enough.
Thermostatic Air Cleaner
System that heats the air being drawn through the engine air inlet to prevent carburetor icing.
Thermostatic Spring
Bimetal coil spring that responds to engine heat and opens or closes the choke.
Thermostatic Switch
Electrical component that shuts off an air conditioning Compressor when the evaporator temperature approaches the freezing point.
Thermostat Rating
Temperature at which the thermostat opens.
Throttle Body
Section of the carburetor containing the throttle valves.
Throttle Positioner
Device that works with idle air control valve in a TBI system to control idle speed.
Throttle Position Sensor
Device that senses how much throttle is opening or closing.
Throttle Return Dashpot
Diaphragm device that prevents engine stalling when returning from high speed to idle operation.
Throttle Valve
Disc-shaped valve that controls airflow through the air horn.
Timed Injection
System timed to inject fuel as the intake valves open.
Timing Advance
Making the spark plug fire sooner in the compression stroke.
Timing Light
Strobe-like light that makes moving parts appear to stand still, allowing timing marks to be observed.
Timing Marks
Calibrating marks on timing gears or other timing devices.
Timing Retard
Making the spark plug fire later in the compression stroke.
Transducer
A device that changes an action or signal from one medium to another (an electrical pulse into a physical movement, for example).
Transistor
Tiny electronic component that functions as a switch, but has no moving parts.
Trigger Wheel
Rotating component with one tooth for each cylinder.
Troubleshooting Chart
A guide that lists methods for finding and correcting vehicle problems.
Turn Signal Flasher
Bimetallic strip and heater unit that makes and breaks contact to cause on-off operation of the turn signals.
Two-Gas Analyzer
Measuring instrument that provides reading~ of NC and CO levels in exhaust.
Vacuum
A pressure lower than atmospheric, in an enclosed area.
Vacuum Advance
System that provides additional ignition advance when engine load is low at medium throttle positions.
Vacuum Choke Break
A device that uses vacuum to open and close the choke to prevent engine flooding at startup.
Vacuum Delay Valve
Mechanism that restricts airflow to slow down action of vacuum on a device.
Vacuum Gauge
Test instrument used to read negative pressure values.
Vacuum Leak
Loss of negative pressure due to crack or hole in a vacuum hose.
Vacuum Switch
One that opens or closes on a change in vacuum.
Valve Timing
Intervals at which valves open and close, determined by camshaft configuration.
Vaporization
A rapid change of state from liquid to gas.
Vapor Lock
Condition caused by bubbles in fuel due to overheating. Can cause stalling, hard starting, or failure to start.
Variable Resistance Sensor
One with internal resistance that changes in response to changes in a condition (such as temperature).
Variable Venturi Carburetor
One in which the venturi size adjusts to maintain a constant air speed in the carburetor.
Vehicle Sensor
Device that changes a condition into an electrical signal that can be used as an input by a computer.
Venturi
Restriction (narrowed area) in air horn.
Vibration Damper
Heavy, rubber-mounted wheel on front of crankshaft to counter harmonic vibrations.
Voltage
Electrical pressure that causes current flow.
Voltage Drop
Reduction of the amount of current flowing in a circuit.
Voltage Drop Tests
Starting system tests that identify parts showing high resistance.
Voltage Generating Sensor
One that changes voltage in response to external change.
Voltage Regulator
Device used to control alternator output.
VOM
Volt-ohm-milliammeter for determining electrical values.
Watt
Unit of work performed by electrical current.
Wet Charged
Battery that is filled with electrolyte and fully charged at the factory.
Wet Compression Test
Test made by placing small amount of oil in a cylinder with a low reading, to determine whether worn rings are cause of low compression.
Wiggle Test
Physically moving wires and connectors to locate broken wires or other causes of intermittent problems.
Winding
Loop of wire on a motor armature that generates a magnetic field.
Wiring Diagram
Drawings that show relationships of components in an electrical circuit.
Wiring Harness
A group of primary wires enclosed in a protective plastic covering.
Quick Charge Test
A method of determining whether battery plates are sulfated (no longer able to hold a charge).
Most info came from the URL below.
http://www.oddballautoparts.com/Automti ... ts_A_F.htm
