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  #1  
Old 09-23-2003, 09:20 AM
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trivial electrical question

being the moron that I am I cut a wire unintentionally in the trunk. I twisted the two loose ends back together and put electrical tape over them. question is simply what should I do in addition so as not to worry about the thing starting on fire? Is it sufficient to put tape over them or should they be soldered and then taped or something else? when and why do electrical fires start. thanks for your patience.

cdt
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  #2  
Old 09-23-2003, 09:28 AM
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The best thing to do is go to radio shack and get a crimp type butt splice. You can buy a cheap inexpensive crimp tool and they will be happy to show you how to use it.

The other alternative is to use a wire nut. By stripping about a 1/2" of insulation off each end of the wire you can then twist the two ends together then cut of the excess bare wire. You should have about a 1/4" to 3/8" bare wire now showing. Then use a blue wire nut which is for smaller gauge wire like #16-#22awg. If the wire is larger like #12-#14 then use a yellow wire nut.
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Old 09-23-2003, 09:59 AM
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I prefer using shrink tube. You place it over the wire before you solder the two ends together. You want to make sure you have it far enough from the heat while you are soldering otherwise it shrinks where it is and doesn't cover the splice. I feel other methods are acceptable when you are stuck in the boonies and you are left with little or no choice.

Electrical fires can occur when a positive line shorts to ground and the line is not properly protected for the current that it is being subjected to when shorted.

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Old 09-23-2003, 11:24 AM
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Another vote for solder and shrink tube for a permanent and very durable repair. This joint is also very water-resistant.

However, for splices that are not exposed to the elements, this is certainly overkill. I prefer wire nuts over crimp connectors because they provide a strong and obvious mechanical connection, with lots of contact area. I have seen so many crimp connections fail, I have lost count. Mostly due to bad technique.

With wire nuts, the open end should be wrapped with tape for added strength, and to prevent the remote possibility of something getting in there and shorting it.
One disadvantage is that wire nuts take up a lot of space, and do not lay flat. Can look messy, if aesthetics bother you.

Fire risk is zero on a proper fuse-protected circuit, unless the brief spark ignites something.

Best of luck.
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Old 09-23-2003, 11:34 AM
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Soldering would be the best, sorry to have not mentioned that. However from the sound of the original post I was addressing the ease of repair and crimp spicing is a great choice. It did not sound like you had the necessary tools and supplies to do the more difficult solder joint. I've been an electrician for 16 years, soldered electrical wiring joints went away about 20 years ago except for circuit board repairs. /We've had great success with butt spices on low voltage systems which include fire alarm, security, access control, nurse call systems, etc. If you have the ability to solder, do it, if not don't be afraid of a butt splice, just take the advice of the other reply's here and don't leave any bare wire unprotected.
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Old 09-23-2003, 11:46 AM
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thanks all, I've been soldering pipes in my basement for a couple years so getting the tools will be all I'll need to switch over to electrical soldering (the propane tank won't cut it). I appreciate all of the responses and will go with the soldering and shrink wrap, as it seems like you are all of the opinion that this is a decent way, and my trunk gets wet occasionally with water sport gear being thrown around back there, etc.. One last question, If the circuit that was cut was properly grounded would a fire or other disaster still occur if the live wire was cut and grounded to a metal part of the car?

thanks folks,
CDT
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Old 09-23-2003, 11:56 AM
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I solder and use shrink wrap whenever possible.

From experience, I find that wire joint repair over a period of time will corrode with exposure.

Whenever I have to troubleshoot a problem circuit, it's usually one that was hastily fastened with electrical tape, butt joint, or something stupid like maple syrup! When I remove the offending junction, the wiring has turned green from oxidized copper deposits.

Shorts can also result from wires that aren't protected with additional sheaths or grommets in places where there is a probablility of pinching.

Fires usually don't result from shorted wires arcing to exposed metal, but when the heat from such activity is enough to ignite the insulation, the surrounding material in the area or fluids, then you have a potential for a fire. Automotive wire is designed to withstand the heat from electrical shorts, but speaker wire is not, and I have seen some people use it as an alternative to supply power to such high amperage components such as fog lamps, car amps, etc!!

Fires can also result from damaged wire being replaced with one of lesser gauge and insulation. I recall once how a friend couldn't get his Bimmer started, and when I investigated, I discovered that he had spliced the aging ground lead with 20-gauge wire!!! The condition of the insulation (which appeared to have suffered meltdown from the current that it was required to handle) made me realize that not being able to start the car probably saved him from an untimely engine inferno!
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Last edited by G-Benz; 09-23-2003 at 12:03 PM.
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Old 09-23-2003, 12:07 PM
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Quote:
Originally posted by tunk
One last question, If the circuit that was cut was properly grounded would a fire or other disaster still occur if the live wire was cut and grounded to a metal part of the car?
CDT
These are somewhat disconnected questions.

The circuit that was cut is now completely divorced from its normal path to ground, so 'properly grounded' does not apply.

If the live cut wire finds a NEW path to ground, it will quickly draw more current than the fuse will allow, and the fuse will blow. No fire potential in this scenario.
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Old 09-23-2003, 01:27 PM
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thanks csnow and the rest for helping me get those basics

cdt
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