Hi,
When the AC unit is on, there is a clicking(loud dripping?) noise near the drain pipe/pan. The pipe goes from the coils(above the furnace) to a black drain pipe near the washer and dryer. If I put my hand under the white pipe, then the sound cannot be heard. The white pipe goes into a black drain pipe and it is open(there is no cap between the two).

My AC unit, 3 years old York, has had a freon leak problem for the last 2 years. Towards the end of last summer, it was not cooling properly, so the company that installed came by and said there might be a leak. It was very hot that week, so they refilled the freon and said that they can check the leak next May(May 2009). They came by today and refilled the freon again and put in some red dye? in order to locate the leak. They also did a pressure check with the unit off and said all of it came back out, so there is no leak inside the house and that it is mostly the condenser. It is not a problem because there is a warranty to the condenser. So, they refilled the freon with the dye and said they will be back next week.

What is causing the clikcing noise? Any idea if the Freon leak is from the compressor? Could it be some other problem? Thanks in advance.

Video here on youtube(clicking noise):
http://www.youtube.com/watch?v=IgJefOhIrFU

Pictures here(white pipe goes from coils to drain cup):
http://picasaweb.google.com/tennisfan20/UntitledAlbum#