I don't know anything about the aux pump, but you definately have a prob if the AC is coming on no matter which button you hit. It should never come on when the furthest-right button, (next to the "Off" button) is pressed. So you may just be having a control problem. But beyond that, I'm out of help for ya. I haven't delved into the CCU controls for these cars that much.
Best of luck. Let us know if/when you figure it out.
