Ratings: +0 / 0 / -0. The Rear Window heater/defroster in my 2008 E92 will not work when the battery is low on charge or old. I understand this is a common issue related to the Intelligent battery sensor which ceases to supply certain services when the battery is below a certain level of charge.however I installed a new battery lately but the
The issue is the the cables attaching the fuse box are bad and corrode causing the connection to drop. This causes the complete no power but when you go to the battery all is fine. The way you confirm is next time this happens, open glovebox, remove fuse panel, grab the fuse box and shake it. Thoroughly clean the glass round the break, taking care not to damage the element further. Stick down some masking tape along each side of the broken element, along the length you intend to repair. Apply a coat of conducting paint to the break. Leave it to dry for 20 minute, then apply a second coat. Remove the masking tape.