Central AC not cooling

I get air from all my vents but it's not cool. The fan on the outside unit seems to blow as strong as it always has, and it's not making any unusual noises. So far I have cleaned the filter, removed the panels on the unit outside and cleaned the fins. I also checked the ductwork in the attic for leaks.
I have not tried to clean the inside coils located in the ductwork yet.
At the top of my air handler inside the house there are three lines going in, two copper and one plastic. Two are insulated and the middle one is not. It looks like there is a green corrosion stain on the middle one, and drip marks on the insulation below. Please see the pics with the links below.
The green drip marks look like they are coming from the top copper line, dripping on the middle line, and then falling on the bottom insulated line.
I will probably end up calling a technician but I wanted to understand as much of the problem as I could first. Thanks for any help.
http://i70.photobucket.com/albums/i97/alkjhlakwehakwehflkuawehflkjashdflkjasdhlf/IMG_0014.jpg
http://i70.photobucket.com/albums/i97/alkjhlakwehakwehflkuawehflkjashdflkjasdhlf/IMG_0013.jpg
http://i70.photobucket.com/albums/i97/alkjhlakwehakwehflkuawehflkjashdflkjasdhlf/IMG_0012.jpg
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The top copper pipe is suppose to be cold. The middle pipe is suppose to be hot. The lower pipe is the condensate drain. The green drip marks look nothing out of the ordinary. You mentioned the fan on the outside unit is running. That is just a fan motor, but do you hear the actual compressor running? If the compressor is not running, you will not get cool air.
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I guess I'm not sure what to listen for to know if the compressor is running. If I stand next to it as it is turned on, I hear a loud click and a hum, then the fan seems to drown everything else out. I've let it run for 10 minutes and the top copper pipe is not cold, and the middle one is not hot. Could that mean the compressor is not working and therefore not circulating the refrigerant, or could it mean that there is no refrigerant to circulate, or could it mean either one?
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Ned452 wrote:

from the fan) if it were running. You might have a dead compressor, a dead motor contactor (hope for that), or a loss of charge.
The contactor is relatively cheap.
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CJT wrote:

Not only are they cheap, they are usually easy to replace and, in my experience, tend to fail first thing in the spring after a cool damp winter.
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The compressor usually sounds like a fridge or similiar to a window A/C unit. On your outside unit, there is some kind of electrical junction box ( not the service box on your house with a disconnect switch, the box thats actually on the unit). Sometimes the contactor gets corroded inside. Give it a little whack to see if the compressor comes on. If not, you gotta call a service guy. As the other poster said, if you are low on refrigerant, the compressor will not come on in order to protect itself from damaging itself. There is a pressure switch on the compressor that detects the freon. Of course it could also be that the pressure switch is defective, which is preventing the compressor from turning on. You cant know until the tech hooks up his guages to the unit.
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