Electrical 101 - What every technician NEEDS to know in troubleshooting electrical faults. - Motor Age - Automotive training, certification & parts info

Service Repair

Electrical 101What every technician NEEDS to know in troubleshooting electrical faults.

Publish date: Jan 1, 2009
By: Peter F. Meier
Source: Motor Age

Email|Print|

|Save|License

12 3 4

Diagnosing electrical system faults seems to pose one of the biggest headaches for many technicians. But more and more vehicle systems are going electronic, and the ability to handle these types of repairs is going to have a direct impact on your wallet. Maybe it's because you can't see it, maybe it's because you don't quite understand it. In either case, let's see what we can do together to take some of the mystery out of tackling electrical issues.

What Is Electricity?

The starting — and ending — point for most automotive electrical circuits is the battery.

Simply, electricity is the movement of electrons in the same direction. Direct current (DC) is the movement of electrons in one direction only and is the type of electricity used in the vast majority of automotive systems. Alternating current (AC) is the movement of electrons first in one direction, then in the opposite direction. Alternators produce AC current that is converted to DC for the vehicle's use.

Electron movement occurs when an imbalance is created either by adding or subtracting an electron from an atom. Nature abhors an imbalance, and the atom will try to regain its balance by either shedding the extra electron to a neighbor or stealing one from it. An outside force has to be applied to create this imbalance, and it is called electromotive force (EMF). The most used source of EMF in an automobile is the battery. Here, one pole of the battery has an abundance of free electrons while the other has a shortfall. The difference between the two posts is electromotive potential, or more commonly voltage. Remember this:

Voltage is the measurement of electromotive potential between the two test points.

Don't quite understand that point? Try this experiment: measure the voltage of a battery as you would normally, with your Digital Volt-Ohm Meter (DVOM) leads connected positive to positive and negative to negative.

Voltage measurement on the positive side of a bulb is shown, where voltage is used to overcome resistance.

Now reverse the leads.

Notice how the second measurement is now a negative number? That's because the voltmeter is doing the math for you and telling you the true potential between the two test leads. This is important to understand, as understanding voltage drop testing is based (in part) on this fact.

Complete circuit These are the components of a complete circuit.

Magnetic induction is another means of producing EMF and is used as a means of generating AC voltage in the alternator. As a magnetic field passes by a conductor, electron movement is created in that conductor. It is the change in the strength and speed of the magnetic field that affects this potential. Remember the sine wave from high school? That is a representation of AC voltage changing with the magnetic field — first, the North Pole passes by, then the south.

12 3 4

Peter F. Meier

motorage@advanstar.com

Peter Meier is an ASE-certified Master Technician, member of iATN and full-time tech in Tampa, Fla. His experience reaches back over 30 years, and his contributions to Motor Age reflect a wide variety of experience with almost every make and model. Articles by Peter F. Meier

Got something to say about it? Post it here!

Joe Glassford / Sunriver, OR, UNITED STATES
Posted Jan 08 2009 01:04PM
Excellent article. Will all of the electrical/electronics on today's vehicles, information like this is critical to the "not so electrical/electronic" minded technicians working today. I have devoted my website: www.Vestest.com to the understanding and troubleshooting of vehicle voltage drop. Some very useful free infomation there in additions to books I have written on the subject.

Service Repair

About the Author

Peter F. Meier