[mdoyle]

I had a similar problem to yours, leaking air suspension and a dead battery. As already mentioned the compressor doesn't run with the key off so that's not causing the problem.

What I found is that on occasion when I removed the key, there would be a partial illumination of the instrument cluster- the shift position indicator would be lit as was the red battery light. Putting the key back in and moving it would make them go out but if I was in a hurry and missed it, the battery would be dead as a door nail.

I finally took the column apart and replaced the ignition start switch (covered in another thread). End of problem.

If your airbags are leaking, get those fixed pronto. They don't cost much but the compressor will and leaking bags can spell an early end for it.