As most experienced restorers will tell you that when assessing a vehicle pre-purchase, there is little sense in investing too much time in looking over the electrics system, as little can be learned unless the car is a runner.
Instead, buyers go on the assumption that most if not all of the auto-electric system will need to be replaced, neither a complicated or expensive procedure. The minimum pre-purchase inspection is to examine the state of the wire harness under the hood, in the trunk, and under the dash.
Even if the seller shows their disapproval, each electrical accessory should be tested to make sure they work correctly, taking in the indicators, gauges, dimmer switches and even the horn.
p> Neglecting a vehicle's wiring system will be a recipe for disaster, especially since replacing the system is neither complicated nor particularly expensive.
The electrical system in classic cars is activated once the key has inserted into the ignition switch and turned. The first task for any electrical system comes into play when the vehicle is stationary, when the driver wants to operate a reading light or even the car's radio ( assuming one has been fitted.) Anyone looking at the wiring circuit for 12-volt systems will be surprised to discover that the cables are smaller in diameter than those in a 6-volt system. 
Any vehicle electrical system must be a loop or circuit.
If the loop is not complete, a short circuit will occur, severe enough to destroy the entire wiring system. the battery and possibly even the entire vehicle( in extreme cases.)
Anyone attempting to rewire a car should have a basic understanding of how automotive electrical systems operate. The principle is little different from conventional electronics, in that electricity flows through wires much like water flows through pipes.
A typical automotive circuit is the one used for lighting. Current flows through the wire from the positive pole of the battery to a light socket and bulb. From there it travels by way of the bulb's filament (which provides resistance) then back through the vehicle's sheet metal and frame, through the battery's ground strap and into the negative pole of the battery. The car metal acts as the return leg of the circuit.
That's why, when bare wires in a car auto electric system touch metal, a short develops. And that's the reason why lights and accessories must be grounded to the car's frame or body. A bulb or motor that isn't grounded won't operate as its circuit is incomplete.
A few inexpensive tools are all that are required to rewire most cars with the most invaluable, the owner's manual for the vehicle being restored!
After that, a wire harness relating to for the vehicle's year, a soldering iron, some lux and electronics solder. a wire stripper, some insulating tithing as well as wire strippers and screwdrivers.
Having a mustimeter on hand will also be a big help.
No less important is the vehicle's charging system consisting of the battery, a control box, and generator, all of them linked to a sign on the dash.
The control box regulates the current flowing through the wiring system, reducing the flow to protect the electrical system from overflow.
Starter motors are used to turn over the engine from rest until it is spinning fast enough to operate.
Coming in two variations depending on the age of the vehicle, either Bendix type where the driving pinion or cog is drawn into mesh with the flywheel- or in the pre-engaged version, where the solenoid is fixed to the motor body and is used to push the starting pinion into the mesh.
The Starter Motor, as its name suggests, is a crucial factor in the car's auto electrical system.
The lighting system provides illumination to allow you to see and be seen. After the starter motor, the headlamps are the biggest draw on the power supply. Unlike the starter, the headlights may be in use for many hours at a time.
As with all electric lighting, the lamps rely on the heating effect, and will always be a compromise between brightness and longevity. The biggest problem with classic car lighting systems is usually system corrosion.
The more work carried out in house, the better, as it does not require costly and intricate equipment or in-depth knowledge.
Just a lot of patience and caution.
