ive got exactly the same prob in my VT Acclaim, there is a hissing behind the glovebox, i assume there is a vacuum connection there? and my fan only works on level 1,2 and 3 when its on max it stops? would the resistor be gone in the fan? time for a new one?
I had this problem on my old car (VP). I'm not sure if VT's have them, but my VP had a long steel rod that is connected to the back of the dial you turn to change it between feet / vents / dash etc. The bit that the end of that clipped into was broken (the little plastic clip down near where your left foot would sit on the footrest.