Shorts

Shorts in your wiring will cause your battery to drain power -- either all the time, when a circuit is activated, or only when a certain device is on. Your battery supplies 12 volts to one side of every device, and the other side of the device is hooked up to ground, which is the negative terminal of your battery (or the entire chassis of the car).

Any wire that has 12 volts on it (immediately or through a switch), can rub itself bare and cause a shot to ground (the chassis). Over time vibrations will wear through the insulation of a wire, and will cause current (the flow of electrons between 12 volts and ground (zero volts)). Note: If too many electrons run through the wire, it will get hot and could even melt. Hopefully the circuit is fused and will blow the fuse prior to burning the wire's plastic insulation.

Shorts can cause shorter battery and alternator life. 12 volts is supplied to the starter switch and then from there it is distributed to the fuse box. 12 volts also goes directly to the fuse box. 12 volt distribution goes to such devices as the headlight switch, brake lights, tail lights, radio, power door locks, and power windows. Each of these devices needs to have a non-shorted wire going to the device. Switches and motors could go bad and cause more current to be drawn from the battery then what is normal.

A multimeter is the best device to use to detect shorts. Your the resistance setting and measure the amount of ohms that there is between the (with battery disconnected) postive terminal and the negative terminal). The reading should be very high resistance with every device turned off. Turn on switches (circuits) one at a time until you find a resistance of zero ohms (or very low ohms). Note: Certain devices will be fairly low in resistance such as your starter motor, which will require a lot of current to start the car. Also the headlights should show a fairly low resistance when turned on.

Try wiggling wires to see if the short occurs or goes away. Use electrical tape, rtv, or other to reinsult wires and eliminate shorts. Replace the wire if it has melted or burned, and especially replace the device or repair the situation that cause the wire to become shorted to ground.

In my experience, the starter switch it most likely to go bad. It may get hot through an internal short.

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Safety

P.S. If ever have to jack up the car, remember to block the wheels and put something under the axile to prevent it from falling too far.

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