Volks, if you have to get inside that rubber tube between cab and
door you can unseat it at both ends and scrunch it up to get the
access you need.  *Far* superior to slitting it.  But when you run
your new wire, for heaven's sake do what I did not, and pass a
fishing line along with the wire; because re-seating the tube end
inside the door is an absolute bugger.   I finally succeeded by
compressing it very hard with electrical tape, shoving it into the
hole and then pulling the tape off from inside, then easing it back
so the lip engaged the hole in the sheet metal.

Before I remove that end again I'll try to pass a fishing wire, but
I'm not extra hopeful.  Ten seconds worth of thought and a piece of
string when I had the thing open would have saved a lot of trouble
for next time.

Yours,
David