Automotive electrical shorts can be very time consuming to hunt down and repair. Even more difficult when the fault is intermittent. I recently put together a short video on the method that I use to hunt down electrical problems on vehicles.
I posted the video on YouTube and so far it has been well received. I have embedded the video below for your convenience. One of the things that I discussed was instead of jamming in fuse after fuse that I set up a 12 volt circuit breaker that helps me find the short efficiently.
I have received several requests to show pictures of my homemade short finding circuit breaker and how to assemble and use it. This information is provided below. Also details about another nifty tool called the fuse buddy.
Pictured above are my two most commonly used homemade contraptions. I've included links 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 kit to the left.
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 use. If you are blowing a 20 amp fuse you want to make sure that 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 reason the circuit breaker does not damage the cars wiring is because they are automatic resetting thermal cycling breakers. This concept is further explained in the video.
If you notice in the pictures of my homemade short finders I use insulated connectors whenever possible. When you replace an automotive fuse with a circuit breaker it will not fit directly into the fuse panel (it's to big).
This is why I attached jumper wires to the circuit breakers. The most important part about installing a short finding circuit breaker is you must make sure that the blades do not touch each other. Some guys at work slide a folded matchbook cover between the two terminals. I prefer to use small insulated terminals that plug right into the fuse panel safely.
Instead of making you read along 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 that I was taught in automotive electrical class.DIY Wiring Diagrams and Car Repair Information from Mitchell 1 Manuals.
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 (mini and ATC). There is also a maxi fuse adapter available but this is not included in the 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. 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.
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 than they were back then.
Learn the principles and understand the theory! The payoff will be job security. Give yourself a head start with the video on the left. Self teach the essentials needed to work with electronic circuits. The streaming video has an easy to understand format making this stuff fun to learn.
Give this automotive electrical help page a bookmark or share it with other driveway 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 one provides a more in-depth look at circuit protection devises and the many different kinds of automotive fuses.
The YouFixCars.com 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.