Rear wiper system ?

[rbruce1314]

Make sure you have an alcohol-based screenwash additive. Otherwise the system clogs up with algae after a while, especially if not used regularly. Build-up is almost always algae not dirt (unless you are VERY careless filling up). It's also worth using demineralised water such as defrostings from the fridge or freezer to avoid build-up of scale from hard water