Aux Fan Wiped Out Battery While Parked..

[Derek A.]

This afternoon - took a short run to the store in the 535i. Parked it. Went back to the office. Came out after work and the battery was dead. As soon as I got come juice to the car - I noticed the aux fan was running. I can only assume it ran the last time out ans wiped out the battery.

AC was not on - its 20 degrees outside...Any idea on what to check.

Gotta leave rescueing a dead BMW from a DaimlerChrylser Assembly plant parking lot - how freaking embarassing.

Derek.-

[Martin in Bellevue]

Ya may want to pull the warm relay under the little black box over the driver side strut under the bonnet. I think there are 3 relay's: low, high & ac switching the aux fan on.

[Adnan]

Hi,

One morning, on my way to work, I noticed that the M30 was running just a tad rough. Diagnosing it as I drove by listening while decelerating, etc. convinced me that it wasn't an ignition or fuel problem. Well, turns out the aux fan was running.

Unlike your situation, my fan shut off when I killed the ignition. From the schematics, I concluded that the A/C high/low pressure switch had failed, causing the system to think the A/C was on. Replaced the switch and the problem went away.

I know this doesn't exactly match your problem but it may be a place to start. Begin by disconnecting elements that drive the fan circuit one by one till you find the culprit. The ETM makes it pretty easy to follow the trail.

Hope this helps,
Adnan