'08 savanah vibration and excessive inside heat

After 5 visits to two dealers and my private mechanic, this vibration between 40 and 55 has not been fixed. Feels like unbalanced tires but that’s not the case. The other problem is when I have the interior heat on, the temp drastically increases momentarily when I make turns. Please someone help me here, I’m very annoyed, to say the least!! Chris Parody, Hagerstown, MD