Fan Blower turns on after doors are locked drained battery.

[carloverthepond]

2010 135i.

So last year my fan blower wouldn't shut off but problem went away. Now it's back with attitude.

Whilst the car is running the fan control won't always go to full. An randomly will charge speed on it's own from off to medium. Turned the car off fan stopped after locking the doors it turns itself back on after about a minute. This caused the battery to go flat over night.

So after reading these and other sites general census seemed to be the FSU part #64119265892. Ordered a new one from Amazon generic off brand. Replaced however hasn't fixed the issue. After installing I do have full control of the fan low to high. An it doesn't charge speed on it's own.

However the big issue that's draining the battery is still present. After turning the car off blower turns itself back on after about a minute. If you lock or open the doors blower shuts off but it comes back on after about a minute.

Any ideas what it can be? Do you think it's the generic replacement FSU? What else can cause the blower to turn itself on?

Many thanks really need a fix.

[carloverthepond]

So just been sat in the car for a hour looking checked for OBD trouble codes, none.

However never noticed this before after you lock the car engine start button stays illuminated. After about a minute light goes off and soon as it does that's when the fan blower turns on.

[mr.fabulous]

http://www.1addicts.com/forums/showthread.php?t=1206142

[carloverthepond]

Originally Posted by mr.fabulous

http://www.1addicts.com/forums/showthread.php?t=1206142

Thanks! That's the post that resulted in me replacing the FSU. After reading this post again think I'm going to strip those wires back. Mine don't look bad but who knows what oxidation is under the plastic.

With the FSU disconnected the engine start button illumination shuts off after 10 seconds instead of a minute when FSU is connected.

[carloverthepond]

Well I replaced all three connections to the FSU. Purchased a new HVAC control panel. An changed out the FSU for a generic one off Amazon. Solved nothing. Fan is still constantly on draining the battery. Been three weeks of no AC and still no further along with this nightmare of a project. New had so many issues on a car I've owned.

[carloverthepond]

There are three wires going in to the FSU. Does anybody have a clue what voltage these should read? I'm guessing 12 volt and the FSU reduces it depending on HVAC control panel settings. When I put a multimeter on red and brown it's never a constant 12 volts not even close. When I test past the FSU on the blower side again voltage constantly fluctuates never close to 12v. What could be causing the FSU NOT to receive constant 12v. Any ideas would be a great help really loosing love for this car.

[carloverthepond]

So I replaced the FSU and blower with BMW OEM parts. Still doesn't work, blower stays on even when car is turned off. What's my next step? Any suggestions would be a great help.

[carloverthepond]

Fixed. After pulling everything apart turned out to be the blue connector going into the BCM / IHKA control module. I've cleaned it and wiggled it to seat better. I'm sure this issue will come back and have to replace cable completely but for now it's fixed. An know what to address later.