I have a 2007 Ford E250 cargo van when accelerating the diverter closes the damper on the air-conditioning and it will cool again after acceleration is over. I know it's some kind of vacuum issueWhat the fix for this problem?

I'm not sure that the compressor is actually turning off. Air flow through the vents drops completely during aggressive acceleration/incline. However when there is mild acceleration/incline, I can feel air flow backing off slightly. I also noticed when the air stops coming through main vents that it diverts for a split second to the defrost vents because a piece of paper on the dash blows up during the transition. Another reason I think the compressor continues to run is when air flow returns to the main vent it hasn't lost it's chill whatsoever. I'm assuming if the compressor turned off and back on again, it would have to build back up before peeking. I'm pretty technical minded, as repair appliances for a living. However I don't have a complete understanding as to how this system works.

The AC/Heater register controls are vacuum actuated. There is a vacuum line that runs down the right side of your intake manifold to a vacuum "T", a vacuum check valve and a plastic vacuum canister. The check valve and the canister supply vacuum to the register controls whenever there is a low vacuum condition (such as moderate to heavy acceleration). Typically, the check valve has failed. It looks like a small "F" with a round, flat check valve.

#'s 13, 14 and 15