I have a 2005 H2 hummer that the aircompressor runs when I start the vehicle and close the door. The button is off. I also noticed that it runs sometimes when I stop. Is this normal?

 

the compressor is meant to level the rear end constantly, so it's possible you've got a leak in your airbags and the compressor needs to fill them when you start the truck.or maybe it used up all the air in the door-close-assist mode, which would make it run again.