Automotive wiring diagrams

Watch the Diy automotive wiring diagrams Video at the bottom of the page. Find out how to pinpoint electrical problems
like a pro. My Name is Mark and I am a Certified Master Technician.

Wiring diagrams are drawings of electronic systems. This repair diagram is the quickest way to auto repair success when
dealing with complex electrical problems on any vehicle. On this page you'll find information required to understand,
diagnose and repair difficult car electrical problems!

Don't have time to watch the 5 minute video? Bookmark or favorite the page and come back latter to see it. The clip
outlines the method I use that often uncovers the car problem on the first step.

In the drawings below are some of the most common electrical symbols you will find in automotive wiring diagrams.
Memorizing what these symbols stand for can speed up your understanding of the given circuit which intern leads to
faster detection of system malfunctions.

In the electrical schematics to follow you will see that symbols are arranged in a circuit to reflect the function, power state,
and relative location of various components.

An electrical symbol may have a slight resemblance to the actual component or its main function. Be aware that solid and
dotted lines represent energy that flows in and out of component connection points.

Abbreviated text labels or codes placed next to the symbols and lines aid in providing description. Both All-Data and
Mitchel 1 provide a depository of electronic auto repair schematics related to specific model auto repair. Each section has
links to the diy automotive wiring diagram to decipher the electronic control of that system.

Automotive wiring diagrams basic symbols

Automotive electrical diagrams provide symbols that represent circuit component functions. For example, a few basic
symbols common to electrical schematics are shown as: (1) Switch, (2) Battery, (3) Resistor and (4) Ground.

Note that the switch symbol displays an open or closed circuit path, which is what an actual switch performs. The battery
symbol appears to be made of layers or plates, common to internal battery construction. The resistor symbol appears to
impede energy flow, which is a resistor function.
The G100 ground symbol indicates a connection pointing downward (ground) that dissipates energy. The G100
designation is to help you find this location on the automobile. Factory auto repair manuals provide component location
diagrams that also include grounding locations.

Variations of symbols will exist depending on function or other characteristics. Examples are: Variable Battery symbol (5)
and the Case Ground symbol (6). Electrical repair diagrams are mostly standardized for the above symbols.

Auto wiring diagram advanced symbols

Abbreviated codes on the diagrams provide circuit path and part or component information. The codes or labels may be
used to show circuit connector pin numbers, circuit values or component polarities that will add clarity to the diagnostic
drawing.

These sets of label examples are: (1)A for Amperage or Amps. (2) ORN for wire diameter and color (3)1340 for Circuit
Path ID (4)P for pass through grommet (5)A for Pin ID & Location (6)C1 for Terminal Connector ID (7)B+ for battery
positive.

Automotive wiring electrical symbols

At first glance, a repair diagram may not convey how wires are of many colors and diameters. The diameter of each wire
symbolized may be indicated by a label placed at some point along side its drawn line (1)(0.8).

Being aware of the color of a wire is important.(2) Wire color information is provided as a color code label in this case
black/white. (3)Also shown are common schematic illustrations of wires, (4)wires connected and (5) wires crossed but not
connected.

For consistency most electrical schematics have signal or energy flow from top to bottom. Component inputs on the left
and outputs on the right. Providing an understanding of how a system would function makes the wiring repair diagram one
of the most valuable resources a technician can use in repairing a vehicle.
Automotive Wiring Tips - Using Relays

Things To Consider When Wiring Accessories...

When wiring anything in your vehicle that draws heavy current such as high powered offroad lights or audio amplifiers,
there are a few things to consider. Number one, make sure you use wire that is rated for the amperage that the
accessories is going to pull. It is always better to have wire that is OVER rated rather than wire that is not rated high
enough. If wire is used that is not rated to handle the current that your accessory will pull, the result could be overheated
wires that could melt the insulation or the electrical plugs found throughout your vehicle (see image below), causing a
short or worse yet it could result in a fire. If you know how much current your accessory will draw you can determine what
gauge wire is appropriate for your application.

Personally I like to use wire that far exceeds the current draw of my accessory. It's overkill but in a few applications I've
used heavy gauge stranded industrial wire with water and chemical resistant insulation. That way there is no question as
to whether the wire is rated high enough or not. If this approach is taken, it is very wise to place a fuse at the battery end
as close to the battery as possible. Most wire in a vehicle, if shorted out, will burn up before the battery overheats and
possibly explodes. If wire that is over-rated for vehicle use is used and a short occurs, a short will most likely result in
damage to the vehicle of some sort unless a fuse is put in line as close to the battery as possible. With the fuse there, in
the case of a dead short, the fuse will burn out first before any damage could occur.

Where to Get your Power

The second important thing to consider when adding accessories is to determine where you will get your power. Many
people will consider tapping into the hot wire of an existing circuit using something called a T-tap or quick slide connector,
which are designed specifically for tapping into an existing wire. This is not always a good idea for several reasons. First
and foremost, tapping into an existing circuit puts additional load on that circuit. The additional load placed on a circuit or
wire may exceed the limits of those wires, connectors and fuse. Overloading a circuit will do one of two things. First, it
may blow a fuse. So people will sometimes place a larger fuse in the fuse block to handle the extra load on that circuit.
BAD IDEA! The fuse may hold but the resulting extra current may be more that the wire is rated for creating heat that can
melt wires and connectors and start fires! The connector to the right was overloaded and fused two adjacent terminals
together, causing a short the blew the vehicles main fuse. Before the fuse blew the connector actually started to burn.
The wire that carried the extra load also had melted its insulation and in places was exposed. Luckily for the owner of this
vehicle, it did not result in a fire but in many cases it does.
A better idea....

With accessories that pull a lot of power it is always better to get your power directly from the batteries positive terminal
rather than tapping into the existing fuse block or wiring harness. In most cases the vehicles existing fuse blocks, wires
and connectors are not rated to handle the additional load of high powered accessories such as offroad lights and
amplifiers. If you are the kind of person that likes to add all kind of goodies to your vehicle it might be worth installing an
additional fuse block that handles non-critical items like offroad lights, CB radios, power inverters, audio equipment, etc.
This additional block can then be powered by a heavy duty wire capable of carrying the current required of all the
accessories on the block. Be sure to fuse the block at the battery.

Another important thing to consider is how you control the switching on/off of the power to your accessories. In almost
every case where high current is required, the switch you will use to turn on the power should not handle the load
because most switches are not designed to handle higher amps. The job of switching the power is better left to a relay.
What is a relay? A relay is a device that, through a magnetic induction coil, turns on the power for you. The switch that is
installed in the cab of your 4x4 actually only powers the relay itself which draws very little current. In most installations a
30 AMP relay from Radio Shack (Auto Relay Cat. Number 275-226) will do unless your amperage demands exceed 30
amps. I like to used a lighted switch in the cab to let me know if driving lights are on.

Offroad Lights or Accessory Wiring Diagram using a 4 - Pole Relay Relay

The method I use for wiring the lights and other external accessories, for the most part, follows the diagram pictured
above. As in the diagram a wire is run from a 12 volt power source to the switch in the cab and out to the relay placing a
fuse at the source of the power. (Follow the relay's wiring schematic when connecting the wires to the relay) One of the
relays terminals goes to ground. Then run a heavy gauge wire from the battery to the relay placing a 30 Amp fuse in line
very close to the battery. Do not connect the power to the battery until all wiring is done. Then I run a single heavy
gauge wire out to the lights or other accessory. If installing lights, split it into two leads at the lights. If you do this be sure
the wire is rated to handle BOTH lights since it will carry the current of both. The diagram shows two leads coming from
the relay. Then I run the second wire of the lights or other accessory to a good ground on the frame of the vehicle. If the
wires will not be soldered together and crimped connectors will be used it's a good idea to put a dielectric paste on the
connectors where they come in contact. This will prevent corrosion as time passes ensuring a good connection. Then
double-checked all wiring before plugging in the power.

Ohms Law
Ohm's Law Defined

Ohm's Law defines the relationships between (P) power, (E) voltage, (I) current,
and (R) resistance. One ohm is the resistance value through which one volt will
maintain a current of one ampere.
( I ) Current is what flows on a wire or conductor. Current is measured in (A)
amperes or amps.

( E ) Voltage is the difference in electrical potential between two points in a

( R ) Resistance determines how much current will flow through a component.

( P ) Power is the amount of current times the voltage level at a given point measured in wattage or watts.

V=IxR
I=V/R
R=V/I

Alternative Offroad Lights or Accessory Wiring Diagram using a Relay