A/c compressor kicks on, but no cold air..checked all the fuses and relays. Everything seems fine. Any one knows what could cause this?

It would seem that you have overfilled the freon level.

pressure sensor on condenser

I would suspect the AC compressor cycling switch (located in low pressure line from compressor) or a AC cutoff wide open throttle relay ( in under hood fuse and relay center) would be causing this problem.

Normal pressure with the engine-compressor off is outside air temp. So both gauges would read 70 or 80 or whatever.
When the system is running, normal is 30-50 low and 200-300 high.
One thing that comes to mind to test is the low pressure switch.

the vehicle is equipped with a pressure transducer. the pressure transducer relays info to the ECM to turn the compressor on, the cooling fans on by letting the ECM know how much pressure is in the lines. the problem is it can go bad and show high pressure (over 4 volts) to the ECM and not allow the a/c to work.

Most likely a restriction in the lines causing the compressor to shut down after a breif period of cold air. Check for bad orifice tube or thermal expantion valve.

to hear things like this really bugs me why would any mechanic replace a parts not knowing that is the problem and call them self a mechanic. Going to give you the best run down as I can think of, and at least we know now you have a new compressor and we can leave that out as the problem.
1 check for leaks, If no pressure your compressor will not run. a dye can be added when charged the
system to see any leaks may exist by using black light.
2 check pressure switch & pressostat making sure is not faulty, if it faulty, the switch will not sense
any pressure to kick the compressor on.
3. check AC fuse, making sure is not blown, if blown no power to ac switch
4. check AC relay, making sure is good relay, bad relay compressor will not work or kick on.
5. Make sure your have no moisture or air in the system, system will not operate up to 100% if any
of those items exist in the system, best way to charged the system is to vacum the system out
first removing any moister and air in the systems, keep in mind, air is 02 can convert into
moister/water molecules if its cold enough.
6. expansion valve faulty, this unit usually goes out like compressor do. it sense the temperature,
regulate refrigerant flow to evaporator. everything may run and operate correctly, if this unit goes
bad it will restrict refrigerant flow cycle and evaporator will not get cold.
I would replace number 6, eventhough if its not bad, it need to be place regardless because of the year of your vechicle, cost 5 bucks. Note: My guess, when you push the ac button do you hear the compressor kick on, if not my guess would be 1 and 2. replace.. If your compressor is running than it would be no. 6 and make sure you have lots of feon in the systems. good luck, hope that help some.

Check the A.C>Relay or It could be low or leaking freon

a/c control unit/module seems to be defective!!!!! because its the one that switches on the compressor!

It could be your low pressure cycle switch is going bad. Check the connection to the switch and it's is located on the A/C Accumulator. The other thing to check is the A/C relay and that is located in the glove box. There is a panel in the glove box that say's relay, there is three relays in there and one of the out side relay's out of the three is the A/C. can not remember which one it is. The middle relay is the fuel pump and the other one is the third break light. Switch the two out side relays and see if your A/C get's better. the other thing too is if the R134a is just a little low, and needs to be topped off. Good luck and hope this helps. if your going to try to recharge the A/C system your self, keep in mind not to over charge.