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Automotive resistors

Automotive resistors are what control the current flow in electrical circuits. The definition of a resistor is a device specially constructed to put a specific amount of resistance into an electrical circuit.

You will also find some other automotive components that use resistance to produce heat, and even light.

An electric window defroster is a specialized type of resistor that produces heat for melting ice, snow and clearing fog.

Electric lights or also resistors that get so hot that they produce a glow of light. That light is amplified and focused by mirrors or reflective material.

There are several different types of resistors in automotive circuits and to follow is a short explanation of the most popular.

A fixed value resistor is designed to have a single rating that does not change.

Typically these are used to decrease the amount of voltage applied to components such as an ignition coil.

Car manufacturers use wiring called resister wire, to limit the current flow and voltage in a circuit.

This wire looks much like normal wiring, but is not as good of a conductor and is marked as a resistor.

Automotive variable resistors

Variable resistors are designed to have a range of resistance available through two or more terminals and a control.

Two examples of this type of resistor are rheostats and potentiometers. Rheostats have two connections, one to the fixed terminal and the other one to a sliding contact on the resistor.

Moving the control moves the sliding contact away from the fixed end increasing or decreasing the resistance.

Potentiometers have three connections one at each end of the resistance and one connected to a sliding contact on the resistor.

In this case, moving the control moves the sliding contact away from one end of the resistance but towards the other.

The name potentiometer is derived from the capability of this electrical component to provide different amounts of potential voltage.

A common automotive resistor

Another type of variable resistor is the thermistor type. This is commonly found in modern-day automobiles.

This type of automotive resistor is designed to change its resistance value as its temperature changes. Note the picture to the left is of a ballast resistor not a thermistor (sorry).

A ballast resistor is used in ignition circuits and hi current starting circuits. But a computers coolant temperature sensor is a great example of a thermistor type resistor.

As the temperature rises and fall's the resistance also changes along with the voltage in the circuit. The electronic control unit interprets this signal voltage as a temperature value.

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Now that we know a little bit about the different types of resistors that you will find in automotive circuits.

Let's head back to the automotive electrical page and find out more about automotive circuit operation

The homepage provides an excellent description of what else is available on this car repair website. This next link takes you from automotive resistors to car repair advice

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