Welding helmet lens covered with spatter?

sensors bad

This Helmet is solar powered leave it on your dash to charge it a few hours will work just fine there is no battery the solar cell holds the power Try getting a full charge on it then see if the darkness will adjust .

They aren't too hard to open up and take apart. There's a glass piece the covers the actual lens and I'm guessing that is what broke. Once the flip is in pieces you can remove the glass piece and it will operate fine without it. If you want to replace it, you can either get a broken flip and use it for parts, but there's a pretty sticky, tough ring of tape holding that glass piece in place. You could also try a very clear piece of plexiglass and cut it to size. Haven't tried that one myself, but it may work.

you mean clean the screen ??
any solution designed to work with perspex or acrylic will be perfect. try "uvex" products or those designed for perspex motorcycle crash helmet visors.
i had a few rear projection tvs over the years and normal everyday household polish didnt do mine any harm at all.
also a damp cloth will remove fingerprints but will leave smears. so skip the washing stage and just use an everday household polish without beeswax in it ,cos that puts a waxy coating on it. stay away from any alchohol based products.and if in doubt try the uvex stuff
http://www.envirosafetyproducts.com/product/Uvex-Clear-Lens-Cleaning-Solution-16-ounce-Pump.html available outside the us as well, made for cleaning safety glasses,