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A voltmeter, also called a multimeter, is used to diagnose automotive electrical problems. This essential electrical tool is a must have for every mechanic, including do-it-yourselfers.



What is a Voltmeter?

Without a digital voltmeter, you will find it difficult or impossible to repair even the simplest electrical malfunctions on your vehicle. Attempting to repair an electrical fault without a voltmeter is like looking for a needle in a haystack. Analog voltmeters, test lights, and digital multimeters are inexpensive but essential tools every mechanic should have.

How does a Voltmeter Work?

All voltmeters and multimeters share a few basic functions, giving you the ability to read voltage and resistance on an electrical circuit. Many models also include a conductivity feature that beeps when there’s little resistance between the positive and negative leads.

A simplified version of the voltmeter is called a test light. Although a test light does not give you a voltage or resistance read, it will allow you to determine if a circuit is live or not.

How are Voltmeters Made?

If you’re feeling crafty, there are many tutorials online you may use to build a simple voltmeter at home. A homebuilt voltmeter is unlikely to be as inexpensive (or as rugged) as a store bought one, but you will learn a lot about how voltmeters work internally by constructing one yourself.

Why do Voltmeters Fail?

  • Many voltmeters use AA or 9V batteries. If your voltmeter no longer works, try changing the batteries.
  • Moisture finds its way inside the voltmeter’s plastic case. This fouls the sensitive electronics found in digital voltmeters.

What are the Symptoms of Failure?

  • The voltmeter gives inaccurate readings. For example, you know your headlamp circuit works, but according to the voltmeter there’s no power running through the circuit.
  • The voltmeter fails to power on.

What are the Implications of Failure?

  • A malfunctioning voltmeter or multimeter complicates diagnostic and electrical repair work.
  • You may end up chasing a non-existent electrical problem or fault because of a malfunctioning or broken multimeter.

Basic diagnostic tools like voltmeters are inexpensive, easy to use, easy to buy, and mostly maintenance free other than occasional battery replacement for the digital models.

If you have questions or concerns about voltmeters or any other diagnostic tools, come into your local Pep Boys where we can answer any question, help you find any part, or perform any vehicle service you might need.