What is the refrigerant charge for a u-line co2075dwr?

It sound like your system is low on refrigerant. After you make sure the condenser is clean, and if you have a fan on the condensor that is is operating, check the temperature of the smallest refrigerant line coming out of the compressor about 5 or more inches from the compressor. This is the high pressure line and during normal operation should be around 140 degrees when fully charged. It is my experience about 5 percent of the mass produced refrigerators coming into this country is not charged properly and can cause the symptoms you describe. About 1 percent develop leaks and lose refrigerant. If your line is warm to the touch or barely warm to the touch, you will need to have your system leak checked and recharged by a competent refrigeration tech.
Hope this helps.

the sensor that sits on the evaporator may be faulty

There is no port unless you use a line tap if your refrigerator is less than 10 years old the manufacturer will pay for the repair unless it will continue to leak and compromise your compressor

On your name plate of A/C unit it will say the unit is factory charged with so many ounces of refrigerant. It will say the weight in ounces depending on the length of your line set you may or may not have to add freon. usually if your line set is longer than 20 ft you will have to add freon. The best way to charge an A/c is to wait for a hot day and charge the unit until it sweats back on your suction line the big insulated line. when the line sweats back to the compressor stop charging unit you will be fine. If this helps please rate me and give me a testimonial.

Anywhere from 5 to 10 PSI. Charge the machine and look for frost line coming back to compressor. Overcharge will be evident when the frostline is out of the coil and down the back side to the compressor. Recover (remove) refrigerant until the frost line goes back out of site.

LOW PRESSURE PORT HAS A BLUE CAP ON IT.MAKE SURE YOU ARE USING REFRIGERANT R-134 BLUE CHARGE HOSE.R-12 CHARGING HOSE WILL NOT FIT R-134 SYSTEMS.SEE YOUR CAR HAS R-134 REFRIGERANT SYSTEM. THE EARLY 90S CARS HAVE R-12 REFRIGERANT SYSTEM.YOU NEED R-134 CHARGE HOSE SET.

I usually dont go with a thermometer temp unless it is sitting in a bottle of water. Now drawer units get the air circulating from the freezer fan. Make sure that is running at a good speed. Also make sure the light is going off when the door is closed. Just close the door and pull gasket toward you and see if a light is on. If it is then make sure the switch is working.If not check the freezer for heavy frost.If yes then you have a defrost problem. If no then you need a tech to check the sealed system.

try cleaning a-coil

Do you have the car running while you are trying to charge the system?
And, do you have the can installed on the low side line (larger line)?
Let me know.
Regards

Depending upon the way you charge it you could introduce air into the system. The lines need to be bleed before charging to make sure the refrigerant is in the charge lines and not air. Most folks that do not do this for a living make that mistake.

With air in a 134 system problems will abound. The only way to really charge a system is to use a vacuum pump to pull it down then charge to the correct lever in ounces as provided on the label of the refrigerant u purchase