[billybek]

Clean the condensing coil and fan. Compressed air and a vacuum will make short work of it and not much mess.
Condensing fan operation. If the bearings are on the way out it may not be doing its job adequately.
Evap fan. Ditto
Defrost heaters and timer.
Overloading fridge or freezer.
Before adding a piercing (saddle) valve, check the temperature of the lines.
Suction line should be cool-cold to the touch depending on load.
Discharge line should be hot to the touch.
Liquid line out of the condenser should be warm.
Refrigerators are critically charged. If they are leaking somewhere, it can be a bugger to find and repair.
A long time ago, we would do a frostback charge.
After evacuating (full empty system or after a sealed system repair) charge the system by guess and start up the refrigerator. If there was frost all the way to the compressor after the refrigerator reached temp we would "recover" some of the refrigerant until the frost would melt close to the compressor. It wasn't a perfect science but it worked.