Air Conditioning - A/C not cooling

I have a very old house that I have lived in for about 3 years and never had a problem with the A/C. This year it has not been cooling like it did before. I have a Lennox pulse furnace with a Carrier a/c unit (approximately 12 years old). The a/c will run all day and only cool the house a degree or two. I started with the basics to try and solve the problem. Straightened all the fins in the outside unit followed by power washing the entire unit. Cleaned the A-coil with foaming cleaner and rinsed with water. New furnace filter. The tech topped off the freon and it didnt help. He thought maybe the filter-dryer was plugged so he recovered all the freon out of the system and put in a new filter, and while it was empty also checked the expansion valve for any blockages. The system was then vaccuumed and filled with freon. I have a digital programmable t-stat. High pressure is 175 while low is 75 at approximately 82F. Right now the house temp is 82 and the closest register temp is 69F. Also the top 1/4 of the A-coil does not feel as cold as the lower part. Anybody have any suggestions before I spend a ton of money on this thing? The air is humid but I would think it should be able to cool a couple of degrees in a couple hours, but it wont.

What is the temp drop over the coil at the coil??? Is the fins in the blower wheel clean?? Is Big copper line cold and wet small copper line warm to hot at the outdoor unit

Sounds like a low head pressure. Could be a worn compressor (just speculating here). This needs to be looked at by a good technician. To diagnose any further we need superheat and subcooling numbers.

Thanks for the replys. The information you asked for is:
Inlet temp to a-coil 74F
outlet temp after a-coil 55F
closest register temp 59F
House t-stat temp 79F
Outside air temp 85F-89F and humid
Low pressure line is cold and wet. High pressure line is luke warm.
The furnace blower wheel was dirty, it had sucked a few small pieces of insulation from the furnace. It is now clean. So far it still is taking 2-3 hours to cool a couple of degrees. The tech that I had service the unit is from a good shop and they suggested that the freon may be contaminated and needs to be changed and something about using nitrogen on the lines. Im not sure if the temps are what it should be, or should the register temps be colder. Do I need to let it run for a few days to pull the humidity out of the air? Im not sure on the superheating numbers. I dont want to spend a bunch of money on this unit if I need to get a new one. If I understand correctly, if the compresser is getting weak wouldn't the inline filter have had some crap in it? Let me know if there is anything else you guys can think of before I have to get the checkbook out. Thanks again

Do I need to let it run for a few days to pull the humidity out of the air?

We tell people to let a unit run dont shut it off and back on. Most of the time it can take like 4 to 5 days to start to get the humidity out of a home. Then you will start to feel cooler and push the temp up some. Id say that 19 o drop over the coil is just fine and good

Hmmm. Also agree, the temperature across the coil looks good. If it's very humid, you should see a lot of condensation off the evaporator coil. Is this year's weather different from the previous years? High humidity places a greater load on the system because water releases its latent heat energy when it condenses.

In answer to your question: A worn compressor will not usually cause the filter/drier to become blocked. But a blocked filter/drier can cause compressor damage. On a restricted system, superheat is high and subcooling is high.

Some very old houses need more insulation or have none at all.

If the unit is running most of the time you can just feel if a drier is going bad. There will be a temp diff . From one side to the other side.

Thanks for the replys. I am going to let it run for a few more days and see how it does. I think I am noticing a difference now as it seems to run less even though the temp and humidity are staying consistent. Temp yesterday afternoon at the closest register was 57F so It appears I have corrected something. I will post back in a couple of days. Thanks again