Electrics Intro

By Geoff Kremer

This series of articles will deal with the basic electrical systems, how to improve and modify them.
I will not be delving into complicated theories and systems this will be more of a hints and tips feature. I will give you a little outline of how things work first.

The words!

AMPS is the unit of current and is the quantity of energy flowing . As an analogy itís a bit like engine Torque.

VOLTS is the pressure of the energy a bit like RPM.

WATTS is the amount of actual power that is equated from the above and is equal to Horse Power.

OHMS is the unit of resistance an item presents to the power flowing through it and is the same as Friction.

A SHORT CIRCUIT is when all the available energy, unintentionally bypasses the load.
An OPEN CIRCUIT is when, unintentionally, all the power stops going where you want it.
EARTH or GROUND or DECK is the return for all the electrical energy returning from the load.
LIVE or HOT is the power coming from the source e.g. battery, to the load via whatever bits and bobs, switches etc, you have along the way.


The bits and pieces!

The LOAD is the item you want the electrical energy to power e.g. motors, lamps etc.
A CONDUCTOR is anything that will allow the passage of electrical current. Generally itís metal.
An INSULATOR Is anything that prevents a current to flow. Generally itís anything that isn't metal.
(There are many exceptions to the above rules but for our needs it will hold true.)
A SWITCH is a device that will intentionally control the flow of current.
A RELAY is a modified switch that is controlled by another switch that canít directly handle the demands of the load.
A FUSE is the thing that stops everything catching alight if you have a SHORT CIRCUIT.
(A SPARK PLUG is just the reverse of a fuse, it catches light when the energy reaches a critical point!).

If you can hang on to the above information you wonít go far wrong.


  • DO NOT Run cables through holes without proper grommets.
  • DO NOT Use household wiring.
  • DO NOT Wrap wires around terminals and screws.
  • DO NOT Twist conductors together and then leave them.

  • DO Use the proper materials to wrap a harness.
  • DO Solder terminals onto the conductor.
  • DO Use fuses to protect individual circuits .
  • DO use the correct size of cable for the job.

Depending an what you are going to do here is a list of some ďmust haveĒ tools.
  1. Pair decent side cutters.
  2. Soldering iron, about a 25 Watt iron should do with a decent size tip and make sure itís an English or American one they are the best. Makes are: ANTEX, WELLER, ADCOLA. I would steer away from soldering guns since they are very heavy to use and you just donít have the control. With the iron get a reel of 18 swg /1.2mm 60/40 flux cored solder.
  3. Automatic wire strippers are absolutely invaluable these one handed wire strippers will make things nice and easy. Get the all metal ones if you can.
  4. Test lamp, almost anything from a bulb and two wires to a proper auto electrical one will do.
  5. Terminal crimpers. If you can get it, the Ripaults basic one is best otherwise get one that will suit the terminals you are going to use........more on terminals later.


There are three basic style of terminal used in auto electrics.
Spade.........Bullet.........Eyelet or Ring.

Now Iím very biased when it comes to terminals. I donít like those coloured plastic ones I think they look awful but they are easy to use and easily available. If you can get the Lucas or Ripaults terminals and covers they will give you a more professional finish also they are more reliable and donít overheat. But what ever, do get the right ones.

Bullets come generally in one O.D. size but do come in various I.D. sizes to fit the cables used.

Spade or Lucar terminals come in a variety of blade and cable sizes from 2.8mm to 9.5mm blades the two most commonly used are 6.3mm and for the big stuff 9.5mm.

Eyelet or ring come in all sorts of sizes to fit a variety of cables and screws

As I said before use only cables designed for automotive use. Do not use household wiring...you will regret it.

The job of the cable is to convey electrical energy and the big problem here is resistance over current. All metal has a resistance (ok! what clever clogs is going to point out super conductors?)
and the object of the lesson is to minimise the resistance, So use the right size cable for the job here is a brief list of what can do what. Iíve included the old style sizes as well.

  • 9/030 0.65mm : gauges, side lights, interior lights.
  • 14/030 1 mm : brake and reversing lights, wipers, indicators, light duty sub feeds.
  • 28/030 2 mm : head lights, ignition, horns, radiator fans, medium duty sub feeds .
  • 84/030 6 mm : alternator main feed, main power feed to electrical system.
These cable sizes are just about the only ones you are going to need so I suggest you get a reel of each plus one reel of black 1mm. You wont need the 6mm unless you are going to do a complete rewire. As for colours well it would be wise use a different colour for each job and indeed the Lucas colour code is just about the best there is but are you really going to order 30+ reels of cable just to get a few feet of each colour. Basically so long as you know what wire does what then youíll be ok but here is the very basic body colour Lucas scheme
  • Brown main electrical input feed and charging circuit.
  • Blue head lights
  • Green fused ignition circuits, indicators, brake lights, reveres lights.
  • white unfused ignition circuits
  • Red side lights, dash lights.
  • Mauve horns, interior lights.

Other things

Tie wraps or cable ties are must to have.
Adhesive electrical insulating tape.
Harness tape. Now this stuff is the only tape you should use to wrap a harness in. Basically its the electrical insulating tape but without the adhesive and is the tape most manufacturers use. Do not use the adhesive tape otherwise after a while itíll start to undo, and it leaves a sticky residue behind which you cannot get off so please be warned!
Heat shrink sleeving. It is absolutely invaluable and comes in all sizes. This is the stuff that shrinks to up to a third of itís original size when heated. You can use a small hot air gun or a gas cigarette lighter to shrink the sleeving.

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