Air conditioner problems

My air conditioner will work for a little bit and then after driving awhile it blows hot air air or nothing comes out. I have spent over $1,500.00. I have changed A/C compressor $750.00 another procedure $750.00 that they had to remove dashboard. Also, we hear clicking noise but mechanic said it does not stop acting from working. And now mechanic could not get A/C to act up while at shop. But usually if I drive over an hour it starts acting up. Warm air or nothing. Also it drips hot water on passenger floor.