The fan has a solid-state device that controls the fan speed and is called a final stage and has been known to cause the problems you are having. If you remove the final stage and inspect it and it has large tapered " teeth" that act as heat sinks, replace it with the later version final stage. ♥
November, 23, 2008 AT 3:47 PM
I have an '01 540i and had a similar problem. Shops kept trying to find the problem with no success. Just as I had given up they found a short in the central locking mechanism causing the battery to drain overnight when the car was locked. After replacing this the problem occurred again and after about 2 months in the shop they found a similar problem with the locking mechanism in the passenger door. They are replacing it for free and I will hopefully have no more problems. After months of walking to work and scanning the forums I thought I would share my experience with you in case it helps. Good Luck.