I'm new to the forum, so please forgive me if this has been covered. I couldn't find anything when I searched.
Setting the stage:
I recently purchased a 1920's rowhouse, and I'm working on replacing the knob and tube wiring in the first floor ceiling. The house has three rooms, front to back, each separated by a framed partition wall: living, dining, kitchen. The side (shared) walls are all plaster on brick, so no chance of fishing under baseboards through framing. I tore down the plaster and lath living room ceiling due to damage, but the other two rooms had new drywall ceilings when I moved in. There is a single circuit run of K&T that services a center ceiling fixtures in each of the three rooms. I was able to run new cable up from the basement, through a switch in the living/dining partition wall, and to the ceiling. Now the fun begins...
I had hoped to pull the new cable (I'm using 14-2 and 14-3 MC-Lite) by attaching it to the old K&T wires, which I can access both through the ceiling fixture hole and through the open ceiling in the living room. Unfortunately, I quickly realized that, even though the tubes were all installed with the same orientation (flared end facing the rear of the house), if I attach the new cable to the old wire, the first tube will dislodge from its joist, but then it gets pulled along to the next joist, and the flared end gets stuck. The MC cable doesn't fit through the tube, so I have a logjam: joist, tube, MC cable. It's clear that I have to allow the tubes to drop down out of the way, but I don't see a way of making that happen without losing the connection between the old and new wires. I tried my luck pulling one shorter old wire and then fishing with fiberglass glow rods, but the joist holes don't align particularly well, and it took quite a while to get the rod through 3 joists. I'm dreading the longer runs, which span 4-6 joists.
Is there any way to take advantage of the fact that there is an existing wire running through joist holes before I just yank them and start fishing? I'd thought about taping a tiny, powerful magnet to the old wire, then pulling it and following closely behind with a rod, hoping the rod could "find" the old wire after the tube dropped out of the way, but that seems improbable. Other than that I have no ideas and would sure appreciate a miracle trick.