Hi Norm,
Did you sort the cables for your heater? I'm trying to replace mine and can't figure how to access the one which operates the heater valve from the top slider. You mention that you can't access the screw and that is the same issue I'm finding, no way to get at it with everything where it is. I can see how to enlarge a hole in the glovebox for the screw for the cable from the middle slider, but the valve one has got me stumped! Any suggestions from anyone welcomed!
It's the screw which can be seen in this photo from page 34 of your thread
Also, looking at that I noticed that the control rods cross each other in this photo, is that correct as mine don't seem to cross but run sort of parallel to each other.