I had a short in the headlight circuit. I would think I had it, put in a fuse and blow it. I riged up a ammeter to replace the fuse. If it reads 60 amps, I probably need to hunt some more. It is just an ammeter with leads that will plug into the fuse holder. I have a pic but can't post them on the new HAMB. Saved a bunch of fuses.
I just bumped it on for as long as it took for the needle to start to move. A tenth of a second maybe. No movement, fixed!
Might want to let folks know how dangerous the technique is, since it seems you're suggesting it as a way for other folks to find short circuits. I much prefer using an Ohm meter.
I usually use a light bulb to jump the fuse, as long it is lit you still have the short and if it is a multi function circuit (like on a late model) you can many times determine the actual culprit too. The inline fuse in the tester gizmo pictured is not necessary for this use.
I agree an ohmeter would work fine. I was dealing with two headlights, two cowl lights, two tailights and five dash lights. The diffence in ohms would have been low between the load and the short. I don't have that good of an ohmeter and probably could not have had a solid indication the problem was fixed and I was running out of fuses.
Andy, err...your mention of similar ohm values for a lighting circuit, and a short... I worried that shorts cause wires to melt, (Teflon coat) or when cloth covered, smoke and catch fire. Any part of the harness feel warm? Squirrel is right, 60A is a toaster element waiting to glow.
Everything stayed at room temp. It was only on for an instant. The stuff probably got hotter blowing the fuses than an instant of current. I did not sit there and watch an ammeter pulling 60 amps.I just looked for movement and switched off.
I'm ***uming that 60A is coming from your battery. Before melting anything, maybe swap to a 12V lantern battery that can't deliver that much electricity? Just a thought. When hunting wiring shorts, miniature circuit breakers can be subs***uted for fuses. They'll trip and can be reset. Saves on buying fuses in bulk.
You guys are missing the point. I never said I saw 60 amps. I said, If I saw 60 amps , I need to look some more. I could have said 300 amps. I sure never expected anybody to believe I would run 60 amps continuously thru a light circuit. I thought that it was obvious that I was just looking for a needle movement for a fraction of a second. It was a poor joke intended for people to get a laugh. I wish this whole thread was deleated as it has lost all purpose.
The light globe method is foolproof, simple and works, so I only use that method. It's got to be simple cos my wife says I'm simple for working on cars!
If I understand what your original post says, you would read the amperage of the circuit by that method, no matter the value! By connecting the ammeter in series by way of the fuse block or fuse holder, all you're reading is current through the circuit, and not where that current is going. If it is a ridiculous number, you have a problem, obviously, but what if the number isn't that ridiculous? What if you don't know how much current (amps) SHOULD be flowing through those wires? The best tool/method for finding shorts is a mega-ohmmeter. Using a "megger" p***es high voltage at low current through the wire you're testing and measures the actual resistance of the wire's insulation! A low number equals a short or breakdown of the insulation.Works great, but isn't practical for everyone to buy! For us regular guys, an ohm-meter is the best solution, as some other replies said. Just a word of caution on that though. If you're checking for a short, don't fool yourself into thinking you have a short by reading the resistance of a bulb or rheostat accidentally! In other words, remove the bulb, disconnect the rheostat, etc. in order to verify that the resistance between the power wire and the ground is correct......should be O/L, infinite, REALLY high number, depending on your meter. Something else to look at, since it's quick and easy, is to look inside each light bulb socket for pieces of solder from the base of the bulb. It only takes the tiniest bit of solder to bridge the gap between the power and the case of the socket, and ****! Fuse blown or breaker tripped! I see this on the airplanes I work on pretty often, and only in the past few years has it become fairly common. Maybe poor quality or an "environmentally safer" type of solder on the newer bulbs? Not sure, but more often than not that's the culprit on a lighting circuit! Hope some of this helps
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