2001 Ford Windstar Front Blowers Blow Cold / Back Blowers B

I am having the same problem with my 2003 Windstar. The heater worked fine last winter, but I now experience a loud clicking from the dash when I try to adjust the temp control, and it will only blow out A/C when the heat is on. I have cold air in the back as well. Car Pros, any ideas?

My 2002 windstar had the same problem and when i looked under the hood i found two linkages had come loose, do not know if this is the problem but can anyone tell me where i would hook them back up to. and does anyone know if this could be the problem or a different problem