Does anyone else notice a build up of "residue" when using air con to demist their windows? I've only noticed in cars with air con, it doesn't seem to happen in my vehicles without. I don't think its a lack of cleaning since I generally do it once a week on a Sunday, but Im noticing that on the windscreen there is a residue after using the aitcon that if you wipe it with a paper towel seems to smear on the windscreen. Using glass spray like 20/20 doesn't always clear it on the first pass either, I find im having to use multiple products multiple times to get anywhere.