Ok, I got an odd one here. Customer complaint unit not getting below 15. Cold enough to make ice, not cold enough to freeze ice cream. Unit was working fine for years.
Check unit and sure enough, at 15. Coils looked a little iced, so I set the clock to defrost and checked out. Clock turns fine. Elements heat up fine. Coils melt, clock takes unit out of defrost and I watch - comes down to 15 and stops dead. Hardly any product in reach in. R404A system - so I put on some A1 line taps and check pressures, expecting to see maybe a clogged cap tube. Called True MFG to see what pressures I should be getting - they recommend anywhere from 220 to 250 on hi side, 10 to 14 on low side.
I'm getting exactly 220 and 14, within tolerances. I checked everything - door seals closed, no gaps. Elements are de-energized during cooling cycle. Fan is running. Nothing blocking evap. The ONLY thing I came across as odd was the compressor was red hot - you could not touch it. (Didn't amp it out). Coils spotless. Hate to think I have an inefficient compressor because my pressures are spot on, but anything is possible.