Was running today and the cab fan when on high speed vibrates. When I turn the speed down it is alright. I also want to know were the cab fan is at. Maybe somthing loose? I also was wondering when I have the automatic air control on after a few minutes the little open book sign comes on. If I turn it off then back on somtimes it will work fine for awile then the book comes back on. I cleaned the cab filter inside and out. Any help would be great.