I have a sub zero refrigerator it won't hold the proper temp it fluxuates from 33 degrees to almost 50. It has a new compressor,evaperator a couple new cold controls which the repair man keeps insisting that is the problem but every time he puts a new one in it does the same thing. Any ideas what could be the problem?

Keep the controls in the middle
For example ABCDE keep no higher than C
12345 keep no higher than 3

If you keep them in the D,E, 4 or 5 range it freezes the freon and will not get cold.

Make sure the sensing bulb from the cold control is securley mounted