I have a sub-zero also. These units have two compressors, one for the
fridge and one for the freezer. While I'm just a home owner I just had
mine
serviced. These units are very expensive to replace, $4-6 grand
depending on the model. Based on what the repair had told me,a new
compressor would
cost about $1,000 on my unit. He also said these units can last 40
years
if maintained properly. In the NY area a service call is about $80 just
to
walk in. Sorry to say but it sounds like your freezer compressor
crapped out. Good luck.