I have some good news for you. The problem is not electrical. The issue you are describing is due to a lack of vacuum to the a/c control head. Usually a vacuum line under the hood gets disconnect or broken, causing a loss fo vacuum to the control head. The air blowing out of the defrost and floor vents is a default mode.
Locating the line is not difficult. By looking along the firewall you can find the small hard black plastic vacuum line that supplies the control head. Follow it to where it is broken or disconnected. Repair with a small piece of rubber vacuum line and/or reconnect to vacuum.
Feel free to post again if you need further assistance with this.
The vacuum line goes from a vacuum source in the engine compartment to the a/c controll head. Remove the control head, and disconnect the vacuum harness on the back of the control unit. There should be vacuum to the black line while the engineis running. If not follow that line and look for the break or the lack of connection.
With no vacuum there is no function. If there is vacuum we can check the individual vacuum motors. We need to start at the beginning. and it allstarts with a vacuum supply.
Not exactly sure where the line is. I dont have the diagrams in front me. I am doing this from memory.
Let me know what you find.
First thing you need to do is remove the shield underneath the passengers side of the dash. Once you have that removed you gain access to the vacuum harness connector. remove the connector start the vehicle and listen /feel for vacuum at the black hose.