Since the current cold snap this week, every single morning the rear window has frozen up, and I mean on the inside aswell as the outside. This morning it was dripping onto the rear parcel shelf all the way to work. Left the car parked with sun on rear window and heater on all the way home, parcel shelf not wet, all windows closed, nothing wet in car and just looked outside 11:00 and the rear screen is already iced up again on the inside. Any ideas ? I'm wary of taking the car in and the engineers sepnding many chargeable hours not finding anything.