1998 BMW 323 Auxiliary Fan

Do you mean the blower fan or the auxiliary fan?

The fan is the axuiliary fan not the blower fan. It keeps running even after the engine is shut off and the key is out of the ignition. I pulled the connector off to stop the fan from running.

My 2000 323i just started doing the exact same thing a couple of days ago. I've done some searching and it seems that the temp sensor and relay are built into the variable speed electronics integrated into the fan. If one of these fails, it runs wide open like that. It also seems that this is a common problem with these fans and you have to replace the entire unit. I've been unplugging mine when I'm stopped for a prolonged period of time. I'm considering replacing it myself, but I haven't found a definitive answer regarding the part number to order or exact instructions regarding the swap. All I know is that most report a $400+ bill to have it repaired and I think the fan is a little over half. Anyone done this installation themselves? It looks like there is plenty of room to get it out and in without removing much, I'm just not sure of all the screw locations or the "gotchas" that you don't find out about until you dig in. Hopefully someone can save us the trouble of finding out the hard way?

The part# is 64-50-8-364-093 and the front bumper has to come off to install the fan. Go to Amazon.com and get a Bentley repair manual for your model car.