2004 Ford Escape air conditioner works GREAT when sitting idle. Air conditioner blows HOT air while driving. Seems like the faster I go or the more load on the engine the hotter it blows. Weird huh?
On most modern cars, the engine management system will uncouple the A/C drive clutch when the engine is under high load conditions, such and entering the freeway, pulling a heavy load up a hill, etc. When the engine load lessons, it’ll recouple the drive clutch. Most times, you won’t notice it. In your case, it might just be over reacting to a load on the engine over anything but idle. How has the car been running otherwise? Gas mileage the same, etc?
Since the system uses engine vacuum as one of the load indicators, i’m wondering if you perhaps have a vacuum leak somewhere.
Take the vehicle to a shop and have them check refrigerant charge of the AC system.