I've got a Ford C-Max and as soon as the temperature is below freezing (for most of the past month here in Scotland) the window washers don't work. I bought some super strength screen wash that said it worked to -36C and made it less dilute than instructed for severe winter conditions but still no joy. The jets are supposed to be heated and I sprayed them with de-icer but nothing. I can't think of anything else to try! Any tips??