Getting hard water stains off window

One of the best and safest cleaners for hard water spots is automatic dishwasher (liquid) soap. It's made to dissolve lime and other hard minerals. I use this on my shower stalls in the house about twice a year (we are on a well ... very hard lime water here). Put the liquid soap on a wet sponge and simply wipe. You'll need to repeat and keep it wet, so smaller sections at a time and it will come off and not damage paint for windows. Do not scrub your camper with a scrubbie or anything like that. It will take the paint off. But the automatic dishwasher soap will dissolve very gently. Try it on your glass first if you doubt. Then your painted surface after you've seen it work on the glass. On my shower stalls, I don't use scrubbies either, just a soft wash cloth soaked with the automatic dishwasher liquid.