1988 Dodge Dakota Mopar Express
See if you can find a key online somewhere that will explain what all the symbols tell you in the diagram. That's a big start. Connections will be called out by a "C" followed by a number, splices, an "S" with a number. Ground will look like it has a little lined triangle. Of course, wires are called out by color, such as WH/BL. That's white, with a blue tracer (stripe).
Found one. Not everyone of them "reads" the same, but the symbols are pretty close from this one to others. Just drawn a little different.
BATTERY
Stores chemical energy and converts it into electrical energy. Provides DC current for the autos various electrical circuits.
CAPACITOR (Condenser)
A small holding unit for temporary storage of electrical voltage.
CIGARETTE LIGHTER
An electrical resistance heating element
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
A semiconductor which allows current flow in only one direction.
DIODE, ZENER
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.
PHOTODIODE
The photodiode is a semiconductor which controls the current flow according to the amount of light.
DISTRIBUTOR, IIA
Channels highvoltage current from
the ignition coil to the individual
spark plugs.
(for medium current fuse)
(for High Current Fuse or Fusible Link)
FUSE
A thin metal strip which burns through when too much current flows through it, thereby stopping current flow and protecting a circuit from damage. FUSIBLE LINK
A heavygauge 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
The point at which wiring attaches to the Body, thereby providing a return path for an electrical circuit; without a ground, current cannot flow.
(single 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
An electric device which sounds a loud audible signal.
IGNITION COIL
Converts lowvoltage DC current into highvoltage ignition current for firing the spark plugs.
LIGHT
Current flow through a filament causes the filament to heat up and emit light.
LED (LIGHT EMITTING DIODE)
Upon current flow, these diodes emit light without producing the heat of a comparable light.
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
Current flow activates one or many LEDs, LCDs, or fluorescent displays, which provide a relative or digital display.
MOTOR
A power unit which converts electrical energy into mechanical energy, especially rotary motion.
Normally Closed 
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
A relay which passes current
through one set of contacts or the
other.
RESISTOR
An electrical component with a fixed resistance, placed in a circuit to reduce voltage to a specific value.
RESISTOR, TAPPED
A resistor which supplies two or more different non adjustable resistance values.
RESISTOR, VARIABLE or RHEOSTAT
A controllable resistor with a variable
rate of resistance. Also called a potentiometer or rheostat.
SENSOR (Thermistor)
A resistor which varies its resistance with temperature.
SENSOR, SPEED
Uses magnetic impulses to open and close a switch to create a signal for activation of other components.
SHORT PIN
Used to provide an unbroken connection within a junction block.
SOLENOID
An electromagnetic coil which forms a magnetic field when current flows, to move a plunger, etc.
SPEAKER
An electromechanical device which creates sound waves from current flow.
SWITCH, MANUAL
Open and close circuit, thereby stopping (close) or allowing (open) current flow
SWITCH, DOUBLE THROW
A switch which continuously passes current through one set of contacts or the other.
SWITCH, IGNITION
A key operated switch with several positions which allows various circuits, particularly the primary ignition circuit, to become operational.
SWITCH, WIPER PARK
Automatically returns wipers to the stop position when the wiper switch is turned off.
TRANSISTOR
A solidstate device typically used as an electronic relay; stops or passes current depending on the voltage applied at base.
WIRES
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.
See if you can find a key online somewhere that will explain what all the symbols tell you in the diagram. That's a big start. Connections will be called out by a "C" followed by a number, splices, an "S" with a number. Ground will look like it has a little lined triangle. Of course, wires are called out by color, such as WH/BL. That's white, with a blue tracer (stripe).
Found one. Not everyone of them "reads" the same, but the symbols are pretty close from this one to others. Just drawn a little different.
BATTERYStores chemical energy and converts it into electrical energy. Provides DC current for the autos various electrical circuits.
CAPACITOR (Condenser)A small holding unit for temporary storage of electrical voltage.
CIGARETTE LIGHTERAn electrical resistance heating element
CIRCUIT BREAKERBasically 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.
DIODEA semiconductor which allows current flow in only one direction.
DIODE, ZENERA 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.
The photodiode is a semiconductor which controls the current flow according to the amount of light.
DISTRIBUTOR, IIAChannels highvoltage current from
the ignition coil to the individual
spark plugs.
(for High Current Fuse or Fusible Link)
FUSE
A thin metal strip which burns through when too much current flows through it, thereby stopping current flow and protecting a circuit from damage. FUSIBLE LINK
A heavygauge 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.
GROUNDThe point at which wiring attaches to the Body, thereby providing a return path for an electrical circuit; without a ground, current cannot flow.
(double filament)
HEADLIGHTSCurrent flow causes a headlight filament to heat up and emit light. A headlight may have either a single filament or a double filament
HORNAn electric device which sounds a loud audible signal.
IGNITION COILConverts lowvoltage DC current into highvoltage ignition current for firing the spark plugs.
LIGHTCurrent flow through a filament causes the filament to heat up and emit light.
LED (LIGHT EMITTING DIODE)Upon current flow, these diodes emit light without producing the heat of a comparable light.
METER, ANALOGCurrent flow activates a magnetic coil which causes a needle to move, thereby providing a relative display against a background calibration.
METER, DIGITALCurrent flow activates one or many LEDs, LCDs, or fluorescent displays, which provide a relative or digital display.
MOTORA power unit which converts electrical energy into mechanical energy, especially rotary motion.
Normally Closed
Normally Open
RELAYBasically, 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 THROWA relay which passes current
through one set of contacts or the
other.
RESISTORAn electrical component with a fixed resistance, placed in a circuit to reduce voltage to a specific value.
RESISTOR, TAPPEDA resistor which supplies two or more different non adjustable resistance values.
RESISTOR, VARIABLE or RHEOSTATA controllable resistor with a variable
rate of resistance. Also called a potentiometer or rheostat.
SENSOR (Thermistor)A resistor which varies its resistance with temperature.
SENSOR, SPEEDUses magnetic impulses to open and close a switch to create a signal for activation of other components.
SHORT PINUsed to provide an unbroken connection within a junction block.
SOLENOIDAn electromagnetic coil which forms a magnetic field when current flows, to move a plunger, etc.
SPEAKERAn electromechanical device which creates sound waves from current flow.
Open and close circuit, thereby stopping (close) or allowing (open) current flow
SWITCH, DOUBLE THROWA switch which continuously passes current through one set of contacts or the other.
SWITCH, IGNITIONA key operated switch with several positions which allows various circuits, particularly the primary ignition circuit, to become operational.
SWITCH, WIPER PARKAutomatically returns wipers to the stop position when the wiper switch is turned off.
TRANSISTORA solidstate device typically used as an electronic relay; stops or passes current depending on the voltage applied at base.
WIRESWires 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.