Why does the air conditioning in your 1997 Jeep Cheerokee blow cold but randomly switches from blowing through the vents and the defroster?

vacuum controlled doors ...vacuum leak or a pen or pencil down the vents....look at some pics Everyone should have a manual for their vehicle, and the library should have a professional shop manual available in the reference section(make copies of the right sections) read up and fix it like a PRO! :) good luck