Electrical Wiring Harness Diagram The wire harness (W/H) is systems of electric wires for automobiles to connect all the electronics parts in automobile electrically and work them. As more electronics parts are introduced in automobiles recently, the electric wires used for the wire harness are increasing in number and the structure is becoming more complicated.

The following tables contain detail and description of wiring diagram/harness symbols usually used in the wiring diagram book or manual, check it out:

battery BATTERY
Stores chemical energy and converts it into electrical energy. Provides DC current for the auto’s various electrical circuits.
capacitor condenser CAPACITOR (Condenser)
A small holding unit for temporary storage of electrical voltage.
cigarrete lighter CIGARETTE LIGHTER
An electrical resistance heating element
circuit breaker CIRCUIT BREAKER
Basically a reusable fuse, a circuit breaker will heat and open if too much current flows through it.
Some units automatically reset when cool, others must be manually reset.
diode DIODE
A semiconductor which allows current flow in only one direction.
A diode which allows current flow in one direction but blocks reverse flow only up to a specific voltage. Above that potential, it passes the excess voltage. This acts as a simple voltage regulator.

diode zener

The photodiode is a semiconductor which controls the current flow according to the amount of light.
Channels high–voltage current from
the ignition coil to the individual
spark plugs.


(for medium current fuse)
fusible link

(for High Current Fuse or Fusible Link)

A thin metal strip which burns through when too much current flows through it, thereby stopping current flow and protecting a circuit from damage.


A heavy–gauge wire placed in high amperage circuits which burns through on overloads, thereby protecting the circuit.

The numbers indicate the crosssection
surface area of the wires.

ground GROUND
The point at which wiring attaches to the Body, thereby providing a return path for an electrical circuit; without a ground, current cannot flow.

headlight single filaments

(single filament)

headlights double filaments

(double filament)

Current flow causes a headlight filament to heat up and emit light. A headlight may have either a single filament or a double filament
horn HORN
An electric device which sounds a loud audible signal.
ignition coil IGNITION COIL
Converts low–voltage DC current into high–voltage ignition current for firing the spark plugs.
light LIGHT
Current flow through a filament causes the filament to heat up and emit light.
Upon current flow, these diodes emit light without producing the heat of a comparable light.
meter analog METER, ANALOG
Current flow activates a magnetic coil which causes a needle to move, thereby providing a relative display against a background calibration.
meter digital METER, DIGITAL
Current flow activates one or many LED’s, LCD’s, or fluorescent displays, which provide a relative or digital display.
motor MOTOR
A power unit which converts electrical energy into mechanical energy, especially rotary motion.

relay closed
Normally Closed

relay opened

Normally Open

Basically, an electrically operated
switch which may be normally
closed (1) or open (2).
Current flow through a small coil
creates a magnetic field which either
opens or closes an attached switch.
relay double throw RELAY, DOUBLE THROW
A relay which passes current
through one set of contacts or the
resistor RESISTOR
An electrical component with a fixed resistance, placed in a circuit to reduce voltage to a specific value.
resistor tapped RESISTOR, TAPPED
A resistor which supplies two or more different non adjustable resistance values.
resistor variable rheostat RESISTOR, VARIABLE or RHEOSTAT
A controllable resistor with a variable
rate of resistance. Also called a potentiometer or rheostat.
sensor thermistor SENSOR (Thermistor)
A resistor which varies its resistance with temperature.
reed switch type sensor speed SENSOR, SPEED
Uses magnetic impulses to open and close a switch to create a signal for activation of other components.
short pin SHORT PIN
Used to provide an unbroken connection within a junction block.
solenoid SOLENOID
An electromagnetic coil which forms a magnetic field when current flows, to move a plunger, etc.
speaker SPEAKER
An electromechanical device which creates sound waves from current flow.

switch close

switch open

Open and close circuit, thereby stopping (close) or allowing (open) current flow
switch double throw SWITCH, DOUBLE THROW
A switch which continuously passes current through one set of contacts or the other.
swithc ignition SWITCH, IGNITION
A key operated switch with several positions which allows various circuits, particularly the primary ignition circuit, to become operational.
switch wiper park SWITCH, WIPER PARK
Automatically returns wipers to the stop position when the wiper switch is turned off.
transistor TRANSISTOR
A solidstate device typically used as an electronic relay; stops or passes current depending on the voltage applied at ”base”.
wire not connected
wire connected
Wires are always drawn as straight lines on wiring diagrams.

Crossed wires without a black dot at the junction are not joined (not connected).

Crossed wires with a black dot or octagonal mark at the junction are spliced (joined) connections.

Find the portable format of the above table here (pdf file).

Related terms:

Block DiagramIsometric DiagramWiring DiagramPictorial DiagramSchematic DiagramWire Harness.

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