It appears that I have a similar problem but in a E39 528 with Automatic Air Con. Intermittantly the fan speed ramps to full. Usaully this is for brief 1-2 sec bursts. But recently started to remain in highspeed. The fan speed on the display remains where it was set. Now the fan remains running even when car turned off and key removed. Pulling fuse is the only way to stop it. However in a strange twist sometimes the fan remains controllable but runs very slow even on max speed. Sound very similar doesn't it. Dont know much more at this stage but are hopeing to get hold of electrical diagrams so I can trace properly. Electronic Tech by trade you see
