I have a 93 Dakota and back in the summer I had the ac on. When I would accelerate the cold air would go away. When I left off the accelerator, it came back. Thought maybe it was a vacuum leak but have been told that I have vacuum to the back of the dash. Also, I cannot switch from the defroster vents to the dash vents. Had this issue before and the mechanic tore it apart and greased the baffle. Have been told this time that I need a new heater control panel. Anybody have any ideas or suggestions?