My son has a 2001 Ford F-150 4.6L. When turning on the A/C, it will blow cold for a random amount of time and could be seconds to minutes. Eventually the blower stops and the only way for it to start back up is by letting off the gas pedal. Then the process repeats itself. Any idea why this would be happening?

 

blower stops, or air diverts to defrosters?
everything out of defroster vents only is a sign of a vacuum leak. the heat/ac controls are vacuum operated. defrost vent only is a way to tell if you have a vacuum leak.

 

Thanks for responding! Good question. I'll take it for another drive when he gets back home. My next thought is to check the compressor clutch gap if its not a vacuum leak..

 

Found a small crack in the plastic hose between the vacuum reservoir and the check valve. Threw some black tape over it for now until I can get some replacement hose. Fixed the issue!

 

Took out the battery tray with 4 bolts to get easy access to the vacuum reservoir. Replaced the plastic hose with 7/32 ID hose and replaced the small ~1" length piece on the other side of the check valve. Hope this helps someone.