While working on wiring issues under the dash I found a couple of places that the duct work had cracked and was open at the seam. Being a tight wad and taking a break from the rest I came across this idea and it seems to work out well. Gently remove the duct if you can without making it worse, not always possible. Clean the dust and dirt off with a fairly stiff brush and vacuum. I then coated the edges with Weldwood contact glue and after a few minutes stuck them together. For added sticky, a thinned coating of glue to the outer surfaces makes the next step easier. (Acetone was used for a thinner, no smoking and good airflow) Using black cloth tape I wrapped the duct overlapping the edges and sticking it down into the grooves. Last step was to then brush coat the repair area with black Flex Seal. After it cured, in it went... good as new and still flexible. If you have enough length and the repair area is three or four turns of wire it can be snipped out and glued as before. Can be done with out removing the duct if you have to. Worked for me. Didn't cross post in interiors. Cheers!