Join Date: Feb 2004
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It is a real problem, and a very common one. If the wires are corroded because they were never fully tinned wires, the cores just pull apart and you get left holding a short length of nothing much.
I managed to get around the problem in most areas by running new woring in specific conduits that we installed and deliberately made accessible for future work. It can be made to look attractive, or at least like it belongs.
For the couple of areas where I HAD to follow the old wiring path, I fabricated a tool that was based on something plumbers use to bore out tree roots from pipes.
I used an old cable halyard and crimped on a short lenght of tube at one end so that the tub projected empty for a little way. I then inserted a drill bit that I had machined down the rear of (An 8mm one) so that it fitted into the "socket" of the tube at the end of the cable. A nice flat spot weld to hold it in place and another tube crimped over the other end of the vable (the cable should not be too long, and you should always have the room to run it pretty much straight even when you start the hole.
Use a cordless drill nd a helper to support the middle sections. Dig as much of a pilot tunner in the stuck together conduit as you can with a screwdriver or icepick, insert the drill end and slowly start boring your way through the old wires and insulation. Pulling the whole cable out frequently to clear the debris.
It can go around some fairly noticeable bends, and you always know how deep you have gone by being able to mark the cable and pull it out and lay it along the run to see when you have cleared obstacles andsuch.
A bit of a slow process, but kind of elegant in its solution.
When you have finished, unhook the drill end, tape a really strong messenger line to the cable and pull all the way through. This can either guide your new wires, or iff the hole is too narrow, then you can attach various rasp-like things to further increase the size of the hole. It should even be possible to switch up to a larger sized drill bit and repeat the process now that you have a pilot hole...but we did not need to, so I can only presume that would work.
This is definately a team job, one person ends up sitting in a mess of twisted halayrd cable!
Your helper should be wearing nice sturdy gloves, and preferably eye protection, just in case the cable goes "sproing!".