Questions and Answers

Loading A Circuit For Testing Q. Hi Vincent, I am having a dead short in my electrical system. Whenever I replace a fuse and turn on my lights it is blowing the fuse. I am trying to track it down and came across your idea for putting a load on the circuit. I was wondering if you could provide either more detailed instructions on how your fuse tester idea from your Uncle can be built.

I think I understand but a picture would really help clarify it. I am assuming you use whatever fuse size is appropriate for the circuit? And is there a particular gauge of wire that should be used? Size of lightbulb? Any other precautions before using it? Any help would be appreciated so I can try and track this problem down.

The following is your text just so we are on the same page.

"I prefer the other option, putting a load into the circuit. Now I'd like to say this was my idea, but I got the idea from my Uncle who was a mechanic for over 40 years. It was so simple and elegant that I adapted it for myself and used it with great success for many years. What you need is a old fuse, a bulb and socket and two lengths of wire. They can be as long or short as you like. I took off the plastic from around the end of the fuse and soldered a piece of wire to each end. Then I soldered the socket to the other ends of the wire. I taped it up and I got a little fancy and made up a small cage to go around the bulb. Then I simply plug my modified fuse into the fuse box and there's my circuit load. Now I can troubleshoot the circuit and find the short."

Thanks,
Ryan

A. There is no set parts list for this tester, I used what I had on hand. Mine uses a single element tail light socket and bulb. These are common and can be found anywhere. My Uncle used a head light bulb for his. The reason I didn't use a head light bulb was I was afraid I would drop and break it.

First thing to do is take a blown fuse, doesn't matter what size, we just want to use the contacts, and shave away the corners to expose the metal contact inside. A small wire wheel will expose the contacts and clean them at the same time. Then solder two wires to the exposed ends. I used red wire on one side and when I plug it into the fuse box, I put it so the red wire is on the power side of the fuse. I used 18 gauge wire on my tester.

Then I just solder the other ends of the wires to the wires on the socket. And that's it. The light bulb acts as the load on the circuit and I then start unplugging connectors, starting with the one closest to the fuse box, until the light goes out.

At that point I know the short is between the connector I just unplugged and the next connector, or whatever device is on the circuit.

Electrical Troubleshooting: Part 1

Electrical Troubleshooting: Part 2