Yesterday I tackled the dreaded cord replacement on the shade in the hallway of the rig. The threads posted on the IRV2 web site were invaluable, as was the service tip from the WIT forum.
A couple of noteable issues came up. First, disassembly of the shade is the only way to go. All cords are easy to get to, and the "problems" that caused the cord failure are obivious. I cut the strings off of the plastic hub at the bottom of the shade close to the knot as I could. I measured the length of the unbroken side to get an idea of the length required for the new cords. On a 32" wide by 32" long blind, the cord length was exactly 8 feet long! So to double the cord as required to attach the cord to the spring at the top of the blind took a single length of cord over 16' long. I left it about a foot longer to allow for tying, cutting and threading through the various holes in the blind.
The cord I bought was from "Jo Ann's Fabrics and crafts". They sell a window shade replacement cord that is 1mm in thickness, which is about twice as heavy as the existing cords. It was $4.99 for a package that was 20 yards long. (I bought 2 just in case). I also bought a $2.00 package of "repair needles" to use to thread the cord through the many blind holes and through the 3 metal rails that hold the blind together. The cord was white, but against the taupe colored blind you can't tell the difference.
When I took the blind apart I found that the grommets in the center metal rail had sharp burrs around the edges of the plastic grommets. The normal sliding of the blind simply wore through the cord. Someone here on the site suggested removing and reinserting the grommets from the bottom side to allow the thicker side of the grommet to protect the cord on the edge that it drags on. That turned out to be the hot ticket to prevent a reoccurrence of the cord failure.
Reassembly of the blind was fairly easy, and I used the plastic cord ties to slide onto the loose cord to hold the blinds in a partially open fashion to facilitate rehanging of the shade, which was a little more difficult. Up inside the window vallance there is a plastic clip on one side of the window valance that is intended to hold up one side of the blind while you reinsert the wood screw through the other side of the blind and into the top of the vallance. Due to small work space this took a while. A cordless drill with a 6" bit extender is invaluable for getting to the screws that hold the blinds up.
Afterwards you tie off the strings to the plastic hubs while the blind rests in the closed position. After the cords are tied off, tighten the cords by wraping each side of the blind cords one wrap at a time until the propper tension is achieved.
The blind is now good as new, and it cost me $7.00 including the needles. It took about 45 minutes to do the cord replacement, as I was being careful not to screw it up, or confuse myself. I could do it again in 15-20 minutes.
One side note for someone doing a small blind like mine. It didn't occur to me at first, but on the smaller blinds there are only two sets of holes for the vertical cords to run through. On a bigger blind like in a bedroom or living room, there will be four sets of vertical cord holes. I suppose that I could have just used one cord on each side of the spring to run down through the blind instead of two, since I had to run both vertical cords through the same set of holes in the blind. This was not an issue as there is plenty of room for the cords in the holes in the blind, even for the larger 1mm cord.
Hope this helps someone that is thinking of tackling this repair. It's not as complcated as it first seems.