I have a 1989 190 2.6. My problem is that I continue to get air coming out of my driver and passanger vents when everything is off. The air starts to come out when driving on the express way. The faster I go the more air that comes out. When I have the thermostat on red the air that comes out is HOT and when the thermostat is on blue the air come out COOL. Can someone please help!!

Thanks