How to find a short

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Rondo84

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Good afternoon, I have a question about finding a short in my 97 TJ 2.5.
In the fuse box under the hood, my number 6 fuse (30amp) keeps blowing, when I checked it, the negative side also lights my test light. I lifted the fuse box off and tried unsuccessfully to pull out the wire going to that blade ( red with white stripe) it wouldn’t come out, how do I hook up my wire tracer ? The alligator clip wonk clip onto the fuse receptacle and I thought pulling the wire was best, maybe I didn’t pull hard enough, but I didn’t want to damage anything trying. Any help would be appreciated. Thanks in advance, Ron

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First, one side of a blown fuse will normally always light a test light or show 12 volts with a meter.

I'd start by pulling the ASD relay to see if that stops the fuse from blowing. If that doesn't stop the fuse from blowing I'd remove the connections to the PCM. That fuse powers only the ASD relay and the PCM so I'd focus on those two devices and eliminate one or the other as what's blowing the fuse.
 
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Rondo84 said:
, my number 6 fuse (30amp) keeps blowing, when I checked it, the negative side also lights my test light. I lifted the fuse box off and tried unsuccessfully to pull out the wire going to that blade ( red with white stripe) it wouldn’t come out, how do I hook up my wire tracer ? The alligator clip wonk clip onto the fuse receptacle and I thought pulling the wire was best, maybe I didn’t pull hard enough, but I didn’t want to damage anything trying. Any help would be appreciated. Thanks in advance, Ron
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Fuses don't have a negative side.
If (+) power is supplied to one side and the fuse is good, there will be (+) power out on the other side.

Wires shouldn't pull out from the back until they are released from the front.
Sometimes it requires a special tool.

For testing, you could add a short wire (or paperclip) to your alligator clip.
In a pinch, your alligator clip's teeth will probably pierce the wire's insulation. ;)
 
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Fuses have a line (12V battery positive) and a load (toward the circuit or load that's powered through the fuse).

If I was looking for a dead short I would put my multimeter in resistance/continuity mode, put one lead on the negative terminal or a good ground somewhere, and probe various connections in the circuit until I found one with continuity to ground.
 
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freedom_in_4low said:
Fuses have a line (12V battery positive) and a load (toward the circuit or load that's powered through the fuse).

If I was looking for a dead short I would put my multimeter in resistance/continuity mode, put one lead on the negative terminal or a good ground somewhere, and probe various connections in the circuit until I found one with continuity to ground.
Click to expand...

If you choose to go this route, disconnect the positive terminal of the battery first before checking for shorts to ground.
 
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Placing a 12 volt incandescent lamp in series with a short will prevent the fuse from blowing, and the lamp will illuminate brightly when the short is present. When the short goes away the lamp will go dim (if there is another load present) or completely off. It can be a valuable tool when looking for a short circuit. You can separate different parts of the circuit to isolate the section with the short or even wiggle and tug on wires while you or a helper watches the 12 volt lamp.

Also, you can dissect a fuse and solder leads onto the blades to use for testing purposes. (You can substitute the lamp for the fuse for testing purposes)
 
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Rondo84 said:
Good afternoon, I have a question about finding a short in my 97 TJ 2.5.
In the fuse box under the hood, my number 6 fuse (30amp) keeps blowing, when I checked it, the negative side also lights my test light. I lifted the fuse box off and tried unsuccessfully to pull out the wire going to that blade ( red with white stripe) it wouldn’t come out, how do I hook up my wire tracer ? The alligator clip wonk clip onto the fuse receptacle and I thought pulling the wire was best, maybe I didn’t pull hard enough, but I didn’t want to damage anything trying. Any help would be appreciated. Thanks in advance, Ron

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You cannot pull the wire out there is a release tab held in by the yellow retainer. You probably don’t want to mess with it, if you break the little tab it can be a pain to keep the terminal in. Get a uninsulated spade terminal crimp a wire on and attach the alligator clip ( or cut the insulation off)
 
Rondo84 said:
Good afternoon, I have a question about finding a short in my 97 TJ 2.5.
In the fuse box under the hood, my number 6 fuse (30amp) keeps blowing, when I checked it, the negative side also lights my test light. I lifted the fuse box off and tried unsuccessfully to pull out the wire going to that blade ( red with white stripe) it wouldn’t come out, how do I hook up my wire tracer ? The alligator clip wonk clip onto the fuse receptacle and I thought pulling the wire was best, maybe I didn’t pull hard enough, but I didn’t want to damage anything trying. Any help would be appreciated. Thanks in advance, Ron

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You did not state when it blows, all the time? Intermittently?
As @Jerry Bransford stated, pull the Asd Relay then pull the pcm connections. Have you installed a new battery recently? Could it be pinching the harness? The red/ White wire goes from the fuse through connector c103 and the Dark green/ pink wire goes from the asd relay to the pcm.
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