Air suspension compressor runs with key off
 

I brought my e53 back from Munich on a trailer (on Nov 14 right after the Paris attacks:yikes:) behind our 9-seat tow vehicle. I had lashed the wheels down tight to the trailer, so the x5 suspension was free to cycle as we drove.

Arriving home, I found the battery dead. Odd. I sussed that out the other day whilst putting on the new number plates ... I heard the air suspension compressor start up. The car key was in my pocket at the time.

So all the way home from Munich on the trailer, the compressor must have started up from time to time and depleted the battery. The battery is also weak and slated for replacement tomorrow.

I would think that the compressor would/should be on a switched power circuit. Is that silly of me? Are your cars similarly wired?

If your car goes into sleep mode after 16 mins or whatever it is, then no, your compressor will not come on. If the car is not in sleep mode, then yes, the compressor will come on with out the key in the ignition.

Sounds like your X never went to sleep. Might be because it was bouncing around on a trailer, but I can't confirm this.

That makes sense. I'm familiar with the e70 sleep mode, but didn't know e53s do that too.

So the moral is, disconnect the compressor when towing for long distances. If there is a next time, I'll find that fuse and pull it.