really? I've been operating on the theory that if auto was enabled, it would automatically switch between modes and fan speeds to maintain the temperature indicated, but if you change the fan speed off of auto it would just blow on whatever setting/temperature you have it set on. That's how it works in my crown vic with auto climate - granted, it's an '02, things might have changed a little since then
I'll have to dig out the owner's manual and see what it says.