Use a multimeter

A multimeter is hands down, the most useful tool for automotive electrical diagnosis.

They call this diagnostic tool a must-have for all mechanics, whether they are professional car technicians or do-it-yourself driveway mechanics.

The reason that this is said is because automotive meters are capable of performing many auto repair troubleshooting procedures.

You can take guessing out of diagnosis and only replace failed components. All automobile electrical parts can be tested before replacing.

Relays, switches, circuit breakers, fuses, resistors and coils can all fail at some point. Learn how to test them and a reliable way to do it!

On this page you will learn How to use a multimeter. You will also see 2 reviews of automotive meters I own.

The Actron 3320 at the bottom of this page, I use at home. And I have the Fluke 88 pictured on the right that I use at work. You can’t go wrong with either one but they are very different.

A quick review of the fluke 88. This is more then a meter. It is an auto repair troubleshooter in a box. You can of course do all the things mentioned on this page and many more.

My favorite feature is the inductive rpm hook up. This is great for cylinder balance tests. The fluke manual is almost like a textbook.

It covers everything this car troubleshooting tool can do. And as a side benefit if you happened to read it cover-to-cover I bet you could not only pass the ASE automobile electrical test but also fix even the most complicated car electrical problems.

What can a multimeter do?

On this page, I will review the basic theory behind these three very important electrical measurements and how to hook it up.

The Ammeter is used to measure the flow of current through a conductor, just like a flow meter is used to measure the amount of water flowing through a pipeline.

When the ammeter is connected for testing the circuit has to be broken and the meter inserted into the break so that all of the flow is measured through the multimeter.

This placement of the ammeter is known as in series with the circuit being tested. This is simply the tool is used to complete the circuit.

Since all the electrons in the electrical circuit must pass through the ammeter it will indicate the number of amps per second passing through it.

As in the case of a flow meter which must be connected so that the water flows through it in the proper direction so also must be ammeter be connected in the right direction.

This will require you to connect the positive terminal to the positive side of the circuit and the negative terminal to the negative side of the circuit.

The voltmeter

The water pressure gauge senses water pressure and registers accordingly. The voltmeter senses and registers the voltage drop through a resistance unit. It therefore is also pressure sensitive.

This type of hookup is referred to as in parallel with the circuit. The voltmeter is not inserted into a circuit like the ammeter but rather parallels an existing circuit. Just like a tire pressure gauge checks tire inflation.

The difference then between ammeter and voltmeter hookup is also the difference between a series and parallel circuit. The voltmeter is useful for automotive diagnosis in the same way that a test light is used for quick checks.

The difference between the voltmeter and the test light is that the multimeter provides the flexibility of measuring different voltages as well as being able to calculate voltage drops across components and circuits.

The ohmmeter

The ohmmeter is an instrument designed to indicate resistance directly in ohms.

Connecting a low-voltage and a variable resistor in series obtains this measurement with the meter and it's test probes.

When the probes of your automotive multimeter are connected together, the circuit is completed and a zero resistance reading is indicated.

When the probes are held a part the ohmmeter will read a maximum or infinite resistance. Sometimes this measurement is indicated as OL or out of limits.

This reading indicates that the resistance between the probes is so high that no current will flow through the circuit.

The ohmmeters most common usage would be for measuring resistance of components and also the integrity of automotive electrical circuit's.

Another way that I use ohmmeters is for checking ignition coils. In your car repair manual, you will be able to look up a specification of the resistance of your ignition coil.

You can then test the actual resistance of the coil and compare it to the specifications.

This was just a brief overview of the three main functions of a multimeter. Even the most basic units like the Actron 3320 come with very good instructions on how to use the tool.

The best way to become skilled at automotive troubleshooting is to buy one of these units and become familiar with its operation.

You can pull relays, coils and switches from junk yard cars and test the components to see how it works. Then fry these old car parts or create opens to compare results!

After you use it a couple of times you will see why this can be a mechanic's best friend and stop you from replacing non returnable electrical components that do not need to be replaced in the first place.



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This next page is the home of my automotive electrical section.

You can read through the page is provided and get a strong basic understanding of automotive electrical theory. This next link will take you from this page about the Multimeter to automotive electrical information



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