Still on fridges; Check for "Short Cycling" & "Continuously Running" Compressors.
Some symptoms:
Lack of Refrigerant; Faulty Control; reduced Air flow on Condeser (eg. blocked filters, brocken fan belt.); Blocked Filter/Dryer; High Temp. in refrig. area eg(Doors not shutting properly, damaged door seals.); Themostat controlling at too low a temp; Leaky Compressor Valves;

Now a couple of good ones..... Air Cooled Condeser operating with low Temp. outside air; Evaporator needs de-frosting.
Now you hire a CCTV for this one which nobody admits to!!...LEAVING COOL ROOM & REFRIGERATOR DOORS OPEN...."because I was too busy to close it!!!"

Good luck!

All I Wanted Was A Cup Of Tea!!