Circuit malfunctions may cause several automotive devices to become inoperative. There are only three electrical conditions that can cause an inoperative circuit.
These three conditions are number one an opened circuit. Number two would be a short and number three would be a grounded condition.
Below I will explain each electrical problem in more detail. The reason that you should read the following page is because it will aid you in diagnosis when an electrical component is not working. If you are using a wiring diagram or taking voltage checks on the vehicle understanding the three primary reasons for failure is important.
Whenever there is a complete break or interruption in the normal current path, such as a break in the wiring from the source of power to the electrical unit or even within the unit itself, current will not flow.
In an automotive electric circuit, current normally travels through the wires or cables, through switches, and the device itself such as a starter motor or wiper motor. A break anywhere along this route results in an open circuit and the complete loss of power.
Some electrical manuals will describe this open as infinite resistance in the circuit. An open condition can cause your automotive meter to read out of limits or OL. However the symptoms will appear somewhat different than the typical high resistance circuit.
The difference is that there will be no heat created by this type of infinite resistance because there is no current flow or circuit load. An open circuit or high resistance circuit may occur as a result of a broken wire within the wiring harness.
Keep in mind that loose connections at the terminals of the electrical device, broken leads or damaged circuit boards inside the device itself can cause an open circuit condition as well.
Note that even poor grounded connections between the electrical load and chassis ground could be considered an open condition. Open circuits depending on there type and location can easily create other related and or mysterious circuit malfunctions.
The term short circuit is used to describe another type of problem or condition which can develop into an electrical circuits malfunction. A short refers to a circuit that is completed in the wrong way.
A common example would be two bare wires touching each other, so the current bypasses part of the normal circuit flow. Bypassing part of the normal circuit simply means that the current has found a path of least resistance and a higher current flow is the result.
This can result in a blown fuse, wiring or component overheating, burned parts of a wires installation and damaged electronic components. A shorted electrical circuit causes more current to flow through the conductor than the conductor can handle.
Too much current known as an overloaded circuit causes the conductor to heat up. If the overload is severe or lasts long enough, the wire can melt. The unique smell of burnt wiring insulation is always a sure sign of circuit malfunctions. Note that the wire can melt to the point where it disintegrates and causes an open circuit.
A grounded circuit is similar to a short circuit. In that the current bypasses part of the normal circuit path. But in this instance, by going directly to a ground source. An exposed wire directly touching ground may cause this.
Also part of the internal circuitry within an electrical component can come in contact with a ground source by touching the housing of the unit itself. You have to remember that in many situations electrical components will be case grounded. This simply means that the attaching bolts provide the system ground for the given electrical circuit.
Deposits of oil, dirt and moisture around electrical connections or terminals can provide an excellent path so that the current flows to ground.
This may also cause a grounded circuit condition. Remember that current flows through the path of least resistance in attempting to complete its circle back to ground. These three types of circuit malfunctions are things that you will find as the root cause of your car electrical problems.
You should keep this in the back of your mind when you are using a wiring diagram to diagnose suspected electrically related automobile complaints. Give this circuit malfunctions page a bookmark or share. Then watch some of my exclusive car repair videos from the links below.
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