The refrigerant lines of a mini-refrigerator can get punctured; the refrigerant leaks out and the refrigerator seems no longer usable. An appliance repairman is sometimes able patch these punctures and add new refrigerant. Sometimes a compressor will also need to be replaced, which requires removing old and adding new refrigerant. Adding refrigerant to a mini-refrigerator is tricky and should be done by a properly trained technician. A mini-refrigerator cooling system includes a compressor, a condenser and an evaporator.
Turn the fridge around and look at the label on the compressor to see what type of refrigerant is used. Most likely it will be R12 or R34.
Remove refrigerant with a proper refrigerant capture device, if needed.
Locate the access or service valve. This is typically a T-shaped valve. Braze an access valve onto the compressor if one is not already there.
Vacuum down the system with a vacuum pump.
Screw the refrigerant can valve adapter onto the valve assembly. Attach the charger hose to the suction valve. Put the can in an upright position to keep liquid from leaking into the refrigerant lines. Screw the handle on the top of the valve to pierce the can. Add a small amount of refrigerant. Turn the system on, and continue to add refrigerant in small amounts.
Remove, close and cap the can after the refrigerator is properly charged, and add compressor lubricant/PAG (polyalkylene glycol) oil.