My air conditioning isnt working very well and I see no condensation dripping.The compressor is running and the lines are cold.I can hear water in a fan somewhere.Is it a clog and if so how to do I unstop it?

 

check and see if your cabin air filter is clogged, (year, model) and see if your getting plenty of airflow at the defroster ouput
i have a problem with vacuum leaking and when im on interstate up a hill, it automatically switches over to defrost and i cant feel air anywhere,
check the blower motor

 

Sounds like a bad check valve.

 

I've got a very similar problem that I'm going to have to deal with.

My AC works fine when I first put it on. I'll turn it to high at the highest fan setting. Where the problems come in is when I start to back it down from there. Once I turn the speed down and and turn the coolness down a bit after a while the AC will stop working altogether. You can still hear the fan TRYING to pump air in, but it doesn't work. It also kinda smells like something is frozen. Once I leave it turned off for a little while ( defrosting ?? ) I'll turn it back on and it'll be OK again until I hafta turn it down, and then it all starts again. Also, once I get to where I'm going and I shut the truck down, within minutes there will be a massive water puddle under the truck.

Does anyone have any ideas?

I was told to checksome sort ofdrain lineas it could be clogged, however I don't know where to find it. Any ideas on that one?