1989 Subzero 532; all of the sudden today the freezer is at 40 degrees. The refrigerator is well within the safe temperature zone. Prior to today the freezer was always very cold at about 8/10. There is no iceball on the refrigerator or freezer side. When I press the button on the freezer the freezer fan runs. When I press the button on the refrigerator door the refrigerator fan doesn't seem to run, but both doors suction shut and seal well. The freezer compressor appears to be running noisily, and is quite hot. The refrigerator compressor runs less often and is not quite as hot. The freezer compressor makes a slightly irregular soft chirping type sound when listening with a stethoscope. The timer appears to be working correctly and the gears are turning. I tried rebooting the power. The coil fan is running happily and I keep the coils cleaned fairly regularly.
Repairs in the last four years include: new refrigerator side evaporator, condenser motor assembly, heat exchanger, drier, gaskets, control, timer, and fan.
I would think I would see a big ice chunk somewhere on the freezer side if a leak sprung up somewhere in the sealed system, even if the freezer was not cooling - like it did before on the refrigerator. The sudden nature of this is bothersome, do compressors fail suddenly? Perhaps the sealed system is still sealed, and everything is turning on when it is supposed to, but the compressor just "partially died" and now cannot compress enough? Is this system separate from the refrigerator side? Why would the refrigerator be working fine, and why would the freezer be sort of cool but not frozen?
Any constructive input much welcomed.