92 Ford Econoline AC Problem on Hills

Hello.

My 92 Ford Econoline conversion van has an issue with the Air Conditioning. The AC blows cold. However, when we go up a hill or I accelerate and put any real load on the engine, the AC stops blowing until I ease up. When I looked under the hood this afternoon, there is a lot of condensation on the canister and hoses.

Any ideas what my problem may be?