Hi I'm new to this forum.
I just picked up a 2001 525i.

After a few weeks I noticed that the cabin fan
was running after i shut the car down???

That next weekend I parked the car for about 6 hours
and the battery was dead. I got a jump to get home but
I have been keeping an ear on it it's a faint sound you
can hear it cumming out of the cabin filter boxes in
the engine compartment.

Does anybody have any input I sure would appreciate any
input on this.

Thanks

Welcome, I would charge the battery fully first to see if it is a voltage issue. BMWs rely heavily on steady battery source if it is not consistently high it will cause strange errors. After the battery is fully charged Have it tested.

Thanks for the tip. I do have one question, My brother in law has a 2001 540 he told me he had the same problem a while back and he brought it in to BMW and he told me they replaced a relay. He said they told him this is a common problem with 2001 5 series. What do you think???

Oh one more thing where on this car can I find the relay. It's not like my Porsche 944S there is no panel in the engine compartment. Also do you have any recommendations for a manual seems they don't publish a Haynes manual for this year and model for a 525I?

Maybe You already have had this fixes but You problem is quite common on E39's and E46's and not just on 2001's...The part that needs to be replaced is what BMW calls "BLOWER HIGH SETTING" and is maybe the same as a relay(?). It is the part that controls the speed of the fan.

When this part is going bad the result can be:
- The fan changes speed up and down when it isn't supposed to
- The fan runs in the same speed regardless of manual changes on the display
- The fan runs continously after the car is shut down (this will empty the battery in less than a night...)
- The fan can start and stop when the car has been parked for hours (this will greet You with an empty battery every now and then)

I have had all of the above problems in two E39's and one E46 and a change of the part fixed it. Due to this I also had to change one battery before figuring out what the problem was...

///Ulf

Blower motor final stage resistor . 15 min fix .