How to Find Automotive Electrical Shorts

Homemade Short Finders

Automotive electrical shorts can be time consuming to hunt down and repair. This task is even more difficult when the fault is intermittent.

I recently put together a short video on the method I use to hunt down car electrical problems using a PDF service manual wiring diagram.

I posted the video on YouTube and so far it’s been well received. In fact, it might help you find the shorted area faster.

We embedded the video below for your convenience. One of the things I discussed was instead of jamming in fuse after fuse, I set up a 12 volt circuit breaker that helps me find the short efficiently.

I’ve received several requests to show pictures of my homemade short finding circuit breaker and how to assemble and use it. We provide this information below. Also details about another nifty tool called the fuse buddy that can also help speed up diagnosis.

Download PDF Service Manuals
Download PDF Service Manuals

Pictured above take a look at my two most commonly used homemade contraptions. I’ve included information at the bottom of the page so you can get your own 20 and 30 amp circuit breakers and jumper wires brand-new.

Or you can go for the ready to go short finder kits they sell on Amazon or other trusted vendors. I personally grabbed several different amperage circuit breakers the last time I was at the junkyard.

I recommend testing junkyard breakers with a meter before using them. If you’re blowing a 20 amp fuse you want to make sure you diagnose the problem using a 20 amp automotive circuit breaker.

If you use a larger amperage breaker you can melt or damage the wiring in the circuit that has an electrical short present. The circuit breaker doesn’t damage the cars wiring because they automatically reset with thermal cycling breakers.

Finding Automotive Electrical Problems

Automotive Circuit Breaker

If you notice in the pictures of my homemade short finders, I use insulated connectors whenever possible.

Well at least insulate the hot side of the circuit. When you replace an automotive fuse with a circuit breaker it will not fit directly into the fuse panel, because it’s to big.

This is why I attached jumper wires to the circuit breakers. Please remember the most important part about installing a short finding circuit breaker. You must make sure the blades never touch each other.

Some guys at work slide a folded matchbook cover between the two terminals. This isn’t a really good idea for several reasons. Of, course the best solution remains using a ready made fuse jumper connector set available below.

Because I’m cheap I use small insulated terminals that plug right into the fuse panel safely. Instead of making you read a long page about the method I use to find electrical shorts I thought it would be more convenient for you to just watch the four minute video.

This outlines the method I was taught in an automotive electrical class conducted by the Chevrolet General Motors brand vehicle training center. The instructor became a bit of a mad scientist in his senior teaching years.

He described his thought process as a flow of electrons. Nevertheless, I learned more from him then from any other human on this earth.

Short Circuit Locator Tools

A nice addition to the homemade circuit breaker idea is to hook up with a fuse buddy. It checks circuit amperage draw by plugging into the fuse panel.  As an example, you can monitor blower motor and fuel pump amperage draws among others that could pull to much and burn a fuse.

Plus the fuse buddy has interchangeable test leads to handle the 2 most popular sizes of fuses, the mini and ATC sizes. There’s also a maxi fuse adapter available, but this is not included in the standard kit. The Pro Kit can read amperage draws on both ATC and Mini fused circuits up to 30 amps.

This is useful for finding electrical shorts, because if you plug it into a 10 amp mini fuse location and get a reading of 20 amps draw you know the 10 amp fuse will blow the second you plug it in.

As an added bonus the fuse buddy pro can be used as an all purpose amp meter with the included 30A test clips. It also has a handy data hold feature and auto power off function so it won’t eat batteries.

Benefits of Electronic Circuit Diagnosis

I personally enjoy working on automotive electrical systems. You get to use your brain. Many car electrical problems are like solving mysteries. Electrical work on cars is one of the cleaner tasks.

Starter circuit diagram
Starter Circuit Diagram

As a car technician, there are plenty of dirty and not so fun operations to go around. If you spend some time at becoming an ace when it comes to electrical problems your skills will bring you higher pay and plenty of challenging cleaner car repairs.

My General Motors sponsored electrical instructor all the way back in 1985 saw the advantages of becoming well-trained in automotive electronics. The need for these skills today in my opinion is even more important.

Learn the principles and understand the theory. The payoff will be job security. If you’re thinking about doing this for a living give yourself a head start with my page about how to start an automotive career. This stuff is fun to learn even if you only use it part time in the driveway. Give this automotive electrical help page a bookmark or share it with other DIY mechanics.

Come back and watch the video again or read more articles and see more videos about auto electronics and car repairs. This is one page from my electrical repair module. You can go back to the main page and read through free articles that will further explain diagnosis and theory to help you solve automotive electrical problems.

A closely related page to this electrical shorts article provides a more in-depth look at circuit protection devises and the many different kinds of automotive fuses.

The Homepage for this automobile website provides a short, pun intended, but sweet rundown of the types of tools and information that is available for site visitors.