Subzero 590 freezer temp fluctuations

[Smdiye]

Hi all,

I moved into a home with a 1995 subzero 590 side by side. I noticed the ice cream was intermittently getting soft. I found that the temperature fluctuates from 0 degrees to 30 degrees. When it is on the warmer side, the freezer compressor is not running. I found if I first increase and then decrease the freezer temp it triggers the compressor to come on and it cools down fairly rapidly. This issue keeps reoccurring. There is no frost build up on the coils. Defrost timer seems to advance appropriately when I turn it. Coils are clean. I’m thinking it might be the defrost terminator but not sure.  Any thoughts are appreciated.

[Econo Appliance]

If you had a bad defrost terminator,  the freezer would warm up to 30-50 and stay there.  So forget about defrost.   What you described is like a failing (out of spec) thermostat.     The test for that is to play with the thermostat when the freezer is warm - tap on it with your fingers,  turn the wheel back and forth.   If the compressor fires up then you have a failing thermostat.     (You already did this test, i'm just explaining it as if you didn't).

590 freezer thermostat is # 7015842  (but you should still double check using your actual model # and serial #)

[Smdiye]

On 12/31/2024 at 9:36 PM, Econo Appliance said:

If you had a bad defrost terminator,  the freezer would warm up to 30-50 and stay there.  So forget about defrost.   What you described is like a failing (out of spec) thermostat.     The test for that is to play with the thermostat when the freezer is warm - tap on it with your fingers,  turn the wheel back and forth.   If the compressor fires up then you have a failing thermostat.     (You already did this test, i'm just explaining it as if you didn't).

590 freezer thermostat is # 7015842  (but you should still double check using your actual model # and serial #)

Thanks that makes sense. I ordered the part and will give it a try.