I've just bought a Beldray window vac (cheap version of a Karcher). I'm not very impressed.
I'm not using it for cleaning the windows, but for getting rid of condensation from the bottom and the sides.
It says to use with a downward stroke, but that means you can't get up the condensation at the very bottom of the window, because the handle bangs on the windowsill before the wiper blade makes it to the bottom of the window. If I tilt it more so that the wiper blade can make it all the way to the bottom, it doesn't suck very well because of the angle at which it seems to be designed to work best.
When I run it down the side of the window, there's about half a centimetre at the side of the wiper blade where the water doesn't seem to be sucked up - which is exactly the location of the condensation I'm trying to suck up. I can turn it at 90 degrees and drag it towards the middle of the window, which is more effective, but still needs me to go over it again to get up all the drips it's spread across the window. It doesn't remove the need to use a cloth on every window, though it does mean I only need one cloth for the house rather than two.
Is this a case of operator error, an inherent problem with these things, or the effects of buying a cheapo model?