[Smith1000]

I have a similar problem with a 97 Custom although my AC works fine until about 5 miles from work on my way home ( on the freeway). The AC will switch from the vents to defrost. This is the only time it seems to happen, although it does not happen every day. If I shut it off and turn it back on, it usually corrects it, although this isn't working as well as it used to. If I turn it off and back on AC Max, it will correct it. I'll have to check into the vacuum issue. Maybe this is possibly affecting my gas mileage as well due to a vacuum leak. My mileage has dropped off a few miles per gallon, but tune-ups and other things I have done to it have not helped. I did check for vacuum leaks under the hood about 2 weeks ago, but found none around the engine.