Ford Repair: Dash vents, vacuum leak, vacuum hose

Question
I have a 97 Ford Explorer that loses all AC out of the dash vents when you go up a moderate incline. Once the car levels off, the AC goes back to normal. What could be the problem?
Thank you

Answer
vacuum leak in engine compartment or under dash usually in engine compartment look for loose or cracked hose near harness going inside of truck usually on passenger side rear of engine-find vacuum hose and follow it back to its source of vacuum and make sure its intact the whole way.