I might be wrong, but my recollection is that you can't get just vehicle speed driven ambient air through the system without the system acting in automatic (with fan and temp controls active), with a/c or without a/c. The econ setting just turns off the a/c but leaves the auto controls doing their thing. The auto setting (with light on) turns on the a/c above certain temperatures.
You could set the econ button, and turn the temp setting low. This will try to set the internal temperature of the car with just ambient air, but the fan will still seek a speed setting depending on the temperature you manually set. Play with the temp until the fan runs at it's lowest speed. The only other option is to hit the off button, which seems to cut off all incoming air and shuts the system down completely, and open a window, lol.
I had wondered about the same thing, and playing with the temp setting while on econ is how I do it. I rarely ever use the a/c anyway, except to defog windows in the rain.