my car sat for about 2 weeks as i fixed it, a 90 deville...

and since then, my a/c only blows the top and bottom vents instead of through the middle

i know it might be a vacuum leak, but i didnt find any, is there anything else that might cause it?

you're mode door actuator is gone out if you take to dealor probably cost
500 to 600 bucks to replace by cad standards the only way to replace is to remove dash but theres a better way

The parking brake release is vacuum operated and is on the same vacuum circuit. Does it release properly?

Lucky that I found your site. Today my ac vents started blowing mid warm on driver side while cold on pass side on my 99 Eldo. Funny that you mention above the parking brake? I applied it over the weekend. Did not think about it until now... Dealer has car at the moment , scratching his head for a $90 flat rate. If they cant figure it out , I will have it tomorrow and try to tackle it. I didnt think about checking the park brake . Anyone have anything else to add to this problem?

Uneven cooling (left to right) is a sign of low refrigerant (but not low enough to set a DTC) on dual control sytems (though you don't mention what you have. Updating your profile would be helpful). If you have a set of guages, you may find it low. If not add one can.