The first thing to check is whether the cabin filter is installed correctly and the fresh/recirc change door is operating correctly. Put the HVAC system in recirculating mode, access the cabin filter area behind the glove box, and see if the change door operates smoothly and completely when you put the system back into fresh air mode. There have been a number of reports on here of the 75 degree default when there is a problem with the cabin filter. Too many owners have had the door mechanism broken by someone attempting to access the cabin filter by manually forcing the change door open.