Demonstrate cable size, colour code, wiring and symbols used in auto wiring.

Demonstrate cable size, colour code, wiring and symbols used in auto wiring.

OBJECTIVE

To acquire detailed knowledge about cable size, their colour codes, wiring and different symbols.

INTRODUCTION

The wiring of present day automobiles has become quite complex because of a number of additional electrical equipment and accessories. However, with the use of coloured cables, wiring harness, plastic fibre optics, printed circuits and improved cable connections, wiring installation has been simplified as possible.

CABLE SIZE

Various kinds of cables are employed in the present-automobiles. While selecting the cable size, the voltage is kept in mind. Generally the voltage drop permitted for a particular length of cable under its full current loading capacity is of order of 10%.These days the cables used in automobiles are of the stranded type instead of the single- conductor type. The stranded cables are more flexible than the single one but they are not easily soldered.

COLOUR CODE

The colour coding for electrical system provides a means of circuit tracing for automobile electrician. The majority of motor vehicles conform to the colour coding standard and the knowledge of this is valuable when used in conjunction with the diagram. The colour coding may vary from model to model. But the colour coding adopted for a particular model is clearly given on the marker wiring diagram.

Main Feed Colour:

There are seven main feed colour each of which is allocated to particular circuit. Feed wires are braided in the main circuit colour, switch wires are braided in the main colour but carry also a coloured tracer woven spirally into the braiding return or ground leads are black. 

The seven main feed colours are as follow:

1. BROWN

2. YELLOW

3. WHITE

4. GREEN

5. LIGHT GREEN

6. BLUE

7. RED

8. BLACK

1. BROWN: -It is used for the battery circuit. It is used from the cranking motor switch to the ammeter, to the radio receiver, to the electric clock, to the inspection sockets & to the battery auxiliary fuse.

2. YELLOW: -It is used for the generator circuit. The cable used for generator terminal to the corresponding control box terminal & to the ignition warning light.

3. WHITE: - it is used for ignition circuit & also for other circuit which do not require the fuse’s& are operated through the ignition switch, such as electric fuel pump, starter motor, solenoid switch & so on.

4. GREEN: - it is used for all the auxiliary circuit which is feed through the ignition switch but is protected by fuses. E.g. for the circuit are break stop lamp, the fuel gauge, wind screen vipers the direction indicator etc.

5. LIGHT GREEN:- It is used for Flasher unit circuit to direction indicator light

6. BLUE: -It is used for head lamp circuit.

7. RED: - it is used for side & tail light circuit also used for fog lamp circuit, panel lights & other lamps which are only used when the side lamps are in operation.

8. BLACK: - it is used for earth circuit.

AUTOMOBILE WIRING HARNESS

An automobile may contain as much as half a mile of wiring, in as many as 50 harnesses, with more than 500 individual connections. Wiring must perform under very poor working conditions. Engine heat, vibration, water, road dirt, and oil can damage the wiring and its connections. If the wiring or connections break down, the circuits will fail. To protect the many wires from damage and to keep them from becoming a confusing tangle. The automotive electrical system is organized into bundles of wire known as wiring harnesses that serve various areas of the automobile.

The wires are generally wrapped with tape or plastic covering, or they may be enclosed in insulated tubing. Simple harnesses are designed to connect two components; complex harnesses are collections of simple harnesses bound together.

A cable harness, also known as a wire harness, cable assembly, wiring assembly or wiring loom, is an assembly of cables or wires which transmit signals or electrical power. The cables are bound together by straps, cable ties, cable lacing, sleeves, electrical tape, conduit, a weave of extruded string, or a combination thereof.

Commonly used in automobiles, as well as construction machinery, cable harnesses provide several advantages over loose wires and cables. For example, many aircraft, automobiles and spacecraft contain many masses of wires which would stretch over several kilometres if fully extended. By binding the many wires and cables into a cable harness, the wires and cables can be better secured against the adverse effects of vibrations, abrasions, and moisture.

By constricting the wires into a non-flexing bundle, usage of space is optimized, and the risk of a short is decreased. Since the installer has only one harness to install (as opposed to multiple wires), installation time is decreased and the process can be easily standardized. Binding the wires into a flame-retardant sleeve also lowers the risk of electrical fires.