Gas and Oil Home Heating Furnaces - A/C Heat Pump Unit not cooling properly

I have a coleman heating and air unit(3 ton) that can barely maintain 79 degrees during the day while set on 70 and about the same temp when the temp drops at night to just below 80. The unit was freezing up and we check the air flow and checked for air restrictions. Due to the lower pressure readings we added freon and got the unit working fine. within a couple of days it started again but was not freezing up. The pressure readings at that time at 79 degrees with fairly high humidity(Okla Summer) were 150 over 60. The low pressure line was cool enough to sweat but not near as cold as it should have been. The high pressure line was luke warm to the touch. I eased liquid 22 in by inverting the tank a little at a time until the low side reached 64(about right) but the high side was about 175. The temp at that time was about 82 so I slowly eased in some more liquid, then turn the tank over and added some gas until the low side was reading 68 but could barely raise the high side and the lines were about the same. Tonight at 77 degrees(two days later) we have the same cooling situation(No Freezing), Low side line is cool and wet, high side is luke warm and pressures are 175 over 70. If it were an auto I would be replacing the orifice, but Is it possible that the compressor is damaged inside and causing these readings or is there another possibility?
Thanks for your help.

2 problems.a leak and a bad set of compressor valves.Easy way to check the valves.Run a/c for 15 minutes.Place hand around suction line close to compressor as possible.Shut unit off.The suction line should remain cool.If it warms up the valves are leaking back.REMEMBER USE PRECAUTION AND BE CAREFUL.Your gauges will also tell you.If you run system than shut it off and pressures equalize FAST the compressor is inefficient.What was your compressor amp draw compared to nameplate data?PDF

Clarification needed:

I have a coleman heating and air unit(3 ton) that can barely maintain 79 degrees during the day while set on 70 and about the same temp when the temp drops at night to just below 80. The unit was freezing up and we check the air flow and checked for air restrictions. ****What did you find? The indoor coil can have a clean surface and be clogged between the fins.****

Due to the lower pressure readings we added freon and got the unit working fine. within a couple of days it started again but was not freezing up. The pressure readings at that time at 79 degrees ***indoor or outdoor temp?**** with fairly high humidity(Okla Summer) were 150 over 60. The low pressure line was cool enough to sweat but not near as cold as it should have been. The high pressure line was luke warm to the touch. I eased liquid 22 in by inverting the tank a little at a time until the low side reached 64(about right) but the high side was about 175.

The temp at that time was about 82 ***indoor or outdoor temp?**** so I slowly eased in some more liquid, then turn the tank over and added some gas until the low side was reading 68 but could barely raise the high side and the lines were about the same. Tonight at 77 degrees ***indoor or outdoor temp?**** (two days later) we have the same cooling situation(No Freezing), Low side line is cool and wet, high side is luke warm and pressures are 175 over 70. If it were an auto I would be replacing the orifice, but Is it possible that the compressor is damaged inside and causing these readings or is there another possibility?


It seems likely to me that the underlying problem is low airflow. Is the metering device an expansion valve?

If it is a capillary tube or orifice, adding gas may get the low side temperatures above freezing. The excess gas ends up in the compressor without affecting the head pressure much. ***Check the temperature of the compressor oil sump after 10 or 15 minutes of continuous operation. It should be too HOT to hold onto for five seconds. If it is not HOT, the compressor is being flooded with excess liquid refrigerant spilling out of the evaporator coil. This may be from an overcharge of refrigerant on top of low airflow.

Coil frosting normally will not occur unless the backpressure stays below 48 to 50 psig. (The circulating air keeps it above the frosting point in the coil itself. (The end bends are out of the air stream and will be frosted.)

SUBCOOLING: The liquid line subcooling should be about 10 to 15 degrees below the condensing temperature. ***Example at 170 psig R-22 condenses at 125 degrees:
If the liquid line temperature is between 117 and 125 degrees, the subcooling is between 0 and 8, and the gas charge is probably low.
If the liquid line temperature is 110 to 117 degrees, the subcooling is 15 to 8 degrees, and the gas charge is probably ok.
If the liquid line temperature is below 105 degrees, the subcooling is greater than 20 and the metering device may be restricted or the system is overcharged.

SYSTEM CHARGE: An expansion valve system can be accurately charged by subcooling. The orifice or cap tube system must be charged by SUPERHEAT. The subcooling is still useful information. Always look at it.

is clean and clear.Try this,block off 80% of outdoor coil with a blanket.If head pressure remains the same or goes up just a little your compressor is history.What is your amp draw?How fast did pressures equalize?PDF