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More Fun with Electrical Diagnosis


Pro_Electrical-DiagnosisIn this article, the latest in a series, we gather resources related to the diagnosis and repair of difficult electrical system issues. The articles below deal with a range of issues, from no code diagnostics to diagnosing a faulty alternator, but what they all have in common is the employment of a logical, step-based process using appropriate tools to get to the source of electrical issues.

First Up… No Code Diagnosis

In this article on Diagnostic News, Scott “Gonzo” Weaver provides strategies for effectively and economically diagnosing elusive no-code drivability complaints. As he points out, with today’s sophisticated vehicle control systems, no-code complaints are rarer today than in the past, but are no less vexing when they are encountered. In the article, he cites specific examples, such as vehicles with intermittent stalling and a misfiring Mustang.


Charging System Diagnosis with Scanner Danner

In this extensive video on, Scanner Danner reviews the steps involved in a thorough diagnosis of a charging system problem on a late-1990s Mazda Miata. As he shows in the video, this vehicle provides a great example of why an alternator swap-out or battery replacement isn’t always the answer. In fact, it could be a total waste of time and money.



Understand the Current Path

In this detailed article on, Joe Glassford makes the case for knowing and understanding a vehicle’s current path as a key tool in simplifying electrical diagnosis. As Joe, notes, “It is the current that gets the work done in any circuit. Current (electrons) flows, voltage does not flow.” Joe breaks down the electrical system and the fundamental relationships between voltage, current and resistance, for instance noting the role current plays even in voltage drop testing.


And, While We Are on the Subject of Schematics…

Most of the above articles and videos incorporate electrical schematics as a key tool in electrical system diagnosis. For many of you, this primer on reading schematics by Jerry “G” Truglia on may be old news, but for others it may be just the refresher needed. Here, Jerry breaks down schematics, from colors and legends to abbreviations and tracing, using real world examples to help you become a schematic expert.


The common thread running through all of these resources is the increasing complexity of vehicle electrical systems and the need to be well versed in electrical circuits in today’s service environments. We hope these resources are helpful to you as you wrestle the bear that is the modern electrical system.

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