My washers only work when it is -0.5C or warmer so I have to develop alternative techniques to clean my screen. One that works if the snow is slushy is to drive way too close to the car or van in front of you so that you get covered with spray from its tyres. Then back off with your wipers going. It clears the salt on your screen for at least about 15 minutes IME. It works for me but then you have to know the road you are doing it on so there are no sudden surprised like the car in front braking suddenly. I don't know the problem with my washers. At the last service and MOT it failed on the washers not working properly so the garag emptied them and gave them a good clear out. re-filled them and it worked well for a short time then instead of the passenger's side not working and the dirvers side working great it is now the other way around. They said it had washing up liquid in it but as an ex lex defence rental it had perfect service record and I doubt they never put wrong stuff in I didnt. Halford best since I got it. I used to be able to pump the washer lever and it would clear it in the past now it clogs up too easily. Annoying really because the garage "sorted" the problem out without me saying yes then charged a lot fpor the trouble. Ripped me off big time. Anyway if someone knows how to de-frost and clean out the washers on a below freezing day please let me know. -3C at best today so unlikely to see my washers working for a while. I also drive a diesel that seems to have awful heater and whereas my last petrol car heated up quick and the washers de-frosted after 10 minutes driving the current car doesn't heat up until after 30 minutes and never defrosts the washers out until air temp is about zero.