Sub-Zero 550 Freezer Shuts Off

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Old 02-23-13, 04:34 PM
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Sub-Zero 550 Freezer Shuts Off

I have a 1994-built Sub-Zero model 550 refrigerator - it's the type with freezer on the bottom. The other day I found everything in the freezer totally defrosted - I suspect it had been off for 48 hours or more. Turning the thermostat to a colder temp (from 3 to 5) I could hear the compressor click back on and it's been fine since then (about a week ago).

I know this is a somewhat common problem because my neighbor, who has the exact same model and age refrigerator, experienced the same problem. They were on vacation and arrived home to find a puddle in front of the refrigerator and everything in the freezer at room temperature.

Thoughts on what diagnostics I can perform and/or most likely culprit?
 
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Old 02-24-13, 03:10 AM
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These units use a common condensor coil but two separate compressors.
It's pretty important to keep the condensor coil up top on the unit clean from dust and kitchen grease.

If you just turned up the thermostat and the unit is now working fine.....that would suggest a defective thermostat.
 
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Old 02-24-13, 08:59 AM
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Thanks for the response. I keep thinks reasonably clean up top - I try to do a thorough cleaning once a year or so.

The one thing I'll add is that temperature control has always been erratic with this thing - temps have swung widely without my touching the dial, but never had an episode this bad where it went to sleep and never work up. I guess that only further points to the thermostat though.

Do you know where is the thermostat is located and what's involved to swap out? Obviously I know where the temperature dial is located, but I'm thinking there must be a temperature probe in the freezer portion itself. Two separate parts or one assembly?
 
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Old 02-24-13, 10:46 PM
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Apparently Sub Zero is selling their parts thru their own dedicated parts network.
Please call Sub Zero at 1-800-222-7820 and they will refer you to one of their six authorized parts and service centers.

Sub Zero part # 7014665

You can google the part number to find online parts places that may have it.
expert appliance.com seems to have it in stock.

The control is mounted right behind the knob and has a remote sensing tube that needs to get routed into the freezer. You would just remove the old one and put the new one in same exact place.

Picture courtesy Repair Clinic
 
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Old 02-25-13, 07:55 AM
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Thanks very much for the detailed response. One other thought/question... Do you think there's any chance this could be related to the defrost circuitry? Is there something in that circuit that could over-ride the thermostat?
 
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Old 02-25-13, 09:33 PM
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Yes......the defrost timer absolutely overrides the thermostat.

Based on a set time (every 6-8 hours ?)....the defrost timer will shut off the freezer compressor and activate a defrost heating element for anywhere from 6-10 minutes. The timer ends the defrost cycle and the compressor resumes normal activity.

Do I think you currently have a defrost problem..... no.
You said temps have been varying widely..... that definitely points to a thermostat issue.
Plus....when you turned the temp down on the dial the compressor came on.
 
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Old 02-26-13, 08:37 PM
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Thanks for giving this some more thought - sounds like I should be replacing the thermostat.
 
 

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