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Thread: Fluctuating Freezer Temperature

  1. #1
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    Default Fluctuating Freezer Temperature

    Model Number: SCD22TBL
    Brand: Amana
    Age: 6-10 years

    I believe I have the right model number. I couldn't find something labeled as such anywhere but did find P1303511W L, and searching for that online seems to point to the model number I listed.

    I'm having a problem with a fair amount of temperature fluctuation in the freezer section. It varies from 0F to 35F. I'm not home enough to notice a pattern, but from what I've seen, it doesn't seem to have much of one. The refrigerator side doesn't seem to be fluctuating much.

    I've cleaned my condenser coils which weren't terribly dirty anyway. The condenser fan seems to run okay without getting particularly hot. I took the evaporator panel off once and didn't see any frost buildup. The times I've checked, the evaporator fan seemed to be blowing air okay.

    It seems to warm up quicker that I would expect it to as compared to just unplugging it and leaving the door closed, which makes me think it is due to heat being introduced inside it. I found a post about an ice maker tray staying in heat mode too long that got my hopes up, but after removing the ice maker altogether, it still has the problem. So, that seems to leave the defrosting system.

    Does my logic seem correct here? If so, what part of the defrost system should I start testing and how do I debug it?

    Thanks in advance.

  2. #2
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    That model uses a mechanical defrost timer. It could be sticking when it goes into the defrost cycle, about every 8-10 hours. It could also be the cold control has a bad set of points in it or the diaphragm in it is bad. Is the wide swing on temps a constant thing? In other words, does the freezer go from 0 to 35 to 0 to 35, etc etc or is this an intermittent problem?
    OWNER RICK'S APPLIANCE REPAIR
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  3. #3
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    I found a good page that describes how the defrost cycle works: Appliance411 FAQ: How does a Frost Free Refrigerator's Defrost System Work? I pulled out the defrost thermostat and tested it. My thermometer was showing around 45F at that point, but the thermostat was showing 0 Ohms. While I was holding it, I heard it click and it went to an open circuit. So, I'm thinking that it is sticking and leaving the defrost heater on for the whole cycle, which seems to fit my theory. I went ahead and ordered another one. Thanks for the help, Josh

  4. #4
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    What you just described was correct normal operation for the defrost thermostat. The defrost thermostat is designed to remain closed under 50 degrees and open above 50 degrees. Those thermostats don't get "sticky" points because they're not constantly opening and closing. That refrigerator is designed to remain in defrost during the defrost cycle, approximately 18 minutes and the defrost thermostat should remain closed the entire time. The temperatures in the freezer will climb 20 degrees but for such a short period of time it's not noticeable.
    OWNER RICK'S APPLIANCE REPAIR
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  5. #5
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    I guess I jumped the gun on that one. I should have waited for your reply, Rick. I went ahead and put the new thermostat in just to eliminate that being a possibility. Around an hour or so later, I caught it in the defrost cycle. I watched the temperature climb up fairly quickly to 66.6F. Then, it slowly dropped back down to around 50F as the heat dissipated to the rest of the freezer. My temperature probe is goes through one of the back vents into the back cover where the evaporator coils are, although it is higher up, past the circulation fan. The night I checked the defrost thermostat and then again tonight when I replaced it, I noticed frost build up at the top of the evaporator coils, but none at the bottom. The frost also covered the thermostat. Both of these times would have been toward the end of a normal cooling cycle, within an hour or two of the defrost cycle starting. My timer says it has an 8 hour cycle. The venting in the rear ducting for the air to get to the evaporator coils is at the bottom of the coils. I would think that it would be more natural for the frost build-up to occur at the bottom of the coils, near the vents. When it is in a normal cooling cycle, it does seem to get pretty cool, though I don't know that it always gets down to 0F. Any suggestions as to what to check next? Thanks, Josh

  6. #6
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    You had your temperature probe behind the evaporator cover where the heater is. It gets pretty warm in that space but it doesn't transfer to the freezer section during normal operation. We don't care about any temperatures other than somewhere around the middle of both the refrigerator and freezer section. The defrost system sounds like it's working like it's suppose to. You've cleaned the coils and checked the fans. Let's get back to the frost pattern on the evaporator. If the refrigerator has been running for a while, take the evaporator back off and look at the coils. You should see all the coils frosted with a light coat of frost about 1/32" or less and it should be pretty much even all the way down the coils. Tell me what you see.
    OWNER RICK'S APPLIANCE REPAIR
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  7. #7
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    That's definitely not the frost pattern I'm seeing. I checked it shortly before it reached a defrost cycle. It's mainly frosted at the top of the coils, and of the top, more so toward the back. I really didn't see frost on the lower two thirds of the coils. The defrost thermostat that I just replaced was quite covered with frost. (For anyone not familiar with where it is, it's the part in the top right of the first picture that is sitting on part of the coils that don't have fins.) I took several pictures that are attached. Here are links that will work for at least a few weeks to the full size images as well:
    http://24.225.86.26/frige/img_1786.jpg
    http://24.225.86.26/frige/img_1787.jpg
    http://24.225.86.26/frige/img_1788.jpg
    http://24.225.86.26/frige/img_1789.jpg
    http://24.225.86.26/frige/img_1790.jpg
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  8. #8
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    The first picture told me whats wrong. You have a sealed system problem.
    Refrigerator sealed system problems should be diagnosed by a qualified service technician only. The sealed system consists of the compressor, condenser, evaporator, heat exchanger, filter/drier and R143a refrigerant. Common problems with a sealed system are bad compressors, refrigerant leaks, and system restrictions. Sealed system repairs should be done only by a qualified refrigeration technician certified for type 1 and 2 refrigerants.
    OWNER RICK'S APPLIANCE REPAIR
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  9. #9
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    .....and can be very expencive.
    OWNER RICK'S APPLIANCE REPAIR
    APPLIANCE TECHNICIAN FOR 29 YEARS
    REFRIGERATION SPECIALIST
    ONLINE SERV TECH: ApplianceBlog.com
    CERTIFIED TYPE 1; TYPE 2.....REFRIGERATION SERVICE E.S.

  10. #10
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    I had a service person come look at the refrigerator. The low pressure side was actually at a vacuum. He added refrigerant to bring it back up to normal pressure. Then, he added a sealant (Super Seal ACR) that seals up really small leaks. That was a few days ago. It has been working well since then. The total repair bill was $185. Thanks for your help Rick.

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