BMW E90 Blower Final Stage Unit (FSU) +

The Final Stage Unit is what controls the current going through to your blower. If your blower suddenly stops working or becomes erratic it could well be this unit that is faulty. This one came off an E90 model. They cost about £80 new. There are a number of discussion sites on the web that tell you how easy it is to change the unit, just a couple of screws to remove and it slots in.