One the fan speeds you will have to check the fan resistor , it is a part that the fan switch plugs in and on side of the a/c unit inside the car , its held on by two screws and a plug in the middle that the wires go to the switch , the have coils that reduce the voltage for the fan on of them is broke or burned , you should see it in the front of the case , if you have air blowing out the defrost you have a vacuum problem , car that age may not have the hose hook back up , or the vacuum can is rusted out on the bottom , hope this helps , Blaine