When going uphill, the AC shuts down. Any suggestions on where to look? on 2006 Ford E-350

AC shuts down when driving the vehicle up hill. Heater duct shuts off.

Asked by for the 2006 Ford E-350
To answer your question accurately, I need to know more information. Does it stop blowing cold air? Does it stop blowing any air? Does it just blow out the defrost vents? On wide open throttle, the PCM is designed to shut the A/C compressor off for more power. I don't know what "heater duct shuts off " means.