2000 Ford F-150 AC

Do you mean you hear the fan running, but the air stops blowing from the vents? If so, is it blowing from another area such as the defroster, heater?

Actually, there isn't anything wrong with the AC. That is a good thing because it can get expensive. In this case, you are looking for a vacuum leak. What happens is the vents are actuated by vacuum. If there is a leak, when you have the engine under a load, the intake vacuum drops because you open the throttle plate for extra power. When that happens, then you lower the vacuum to the HVAC system, which is already low due to a leak. As a result, the vents start changing directions.

Check for leaks under the dash to the controler and vacuum controlers. With the engine running, you may even hear a hissing sound from a leak. Also, check under the hood for leaks too.

Let me know what you find. I'm confident that is the problem.

Joe