Heartland Recreational Vehicles Dust fills our 5th Wheel RV and they dont' care and won't fix or respond to us! Elkhart, Indiana

We bought a 2012 Heartland Big Country 3690SL just four months ago May, 2012.  It has already been in the shop 3 times for the same repairs.  We've had both A/c's replaced, wires dragging on the wheels when in route, door that would not lock and various other small items, but the most urgent one is that the unit fills with dust when we go down the road.  You can actually write your name in the dust on the furniture and counter tops.  We reported it to RV Station Colbert Oklahoma where we bought it and to Heartland Recreational Vehicles Elkhart Indiana.  Heartland Customer Service Rep. J.D. Adams requested we send pictures of the dust in the RV.  He stated he would get right back with us.  We still have not heard from Heartland or their Reps and that was over a month ago.  Meanwhile, we took the RV for the third time to RV Station for repairs.  They told us they could not stop the dust from coming in and that we would have to live with it.  We asked for a copy of the work orders and was told by RV Station they would mail them to us after they reworded them. This was over a month ago and we're still waiting for the work orders.  RV Station stated that Heartland told them the dirt was coming from the window vents and that was how they were designed.  We have had two 5th wheels and two trailers and NEVER had dust come in like this one does.  Heartland claims their units are sealed....How can they be sealed if they fill with dust and who knows what else? The first time the unit was in the shop was ONE week after we bought it and they kept it a week for repairs. Heartland does not respond to customers and drags out the repairs hoping the warranty runs out before they are out the expense of repairs.  We are now stuck with a very poor quality RV that fills with dust and is worth less than half of price we paid resell value. We tried to trade it off but can't afford a $40,000 loss on this RV.  This is truly a Lemon product!!