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Thread: Sub Zero 601F won't stop icing up

  1. #1
    Join Date
    Sep 2017
    Location
    Seattle, WA
    Posts
    2

    Default Sub Zero 601F won't stop icing up

    Model Number: 601F
    Brand: Sub Zero
    Age: More than 10 years

    I've got a set of Sub Zero 601R and 601F that I've owned since the house was new in 1999. The 601R (fridge) has been bulletproof. The 601F (freezer) has been great... with the exception of having to completely defrost it about once a year. I keep the condenser vacuumed. I make sure the drain is clear (until it ices up). I've replaced the control board. I've replaced the drain heater. It just keeps icing up.

    There's got to be something I'm missing. Any ideas of what else I can look for or check?

  2. #2
    Join Date
    Jul 2006
    Location
    Murray, Utah 84107, United States
    Posts
    28,229

    Default

    Where exactly is it icing up?? "Once a year" is an odd time. If the evaporator was icing over it would be more often than once a year. OK, I read it again and assume you're talking about the defrost drain under the evaporator. Is that correct?
    Last edited by rickgburton; September 5th, 2017 at 01:57 AM. Reason: added more info
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  3. #3
    Join Date
    Sep 2017
    Location
    Seattle, WA
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    Default

    Quote Originally Posted by rickgburton View Post
    Where exactly is it icing up?? "Once a year" is an odd time. If the evaporator was icing over it would be more often than once a year. OK, I read it again and assume you're talking about the defrost drain under the evaporator. Is that correct?
    Yes, it's the evaporator, and it ices up more than once a year... that's just how often I've been feeling motivated enough to empty it out, pull off the rear panel, and defrost everything.

    The ice seems to start forming near the bottom of the evaporator and then fills the defrost drain. I've replaced the control board, thinking perhaps it wasn't properly initiating the defrost cycle. I've been chasing this problem for years, and keep coming up empty.

    I know there's a way to manually initiate the defrost by holding down the ICE button while the unit is running, but I don't even know if that's the issue. I'm about to empty the unit and defrost it again, but I'd love some guidance as to how/what I should test to find the cause. Voltage on the heat strip? Something else I can test to see why it keeps icing up?

  4. #4
    Join Date
    Jul 2006
    Location
    Murray, Utah 84107, United States
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    To initiate Diagnostic Mode, the unit must be ON. With the unit ON, press and hold either COLDER key, then press the UNIT ON/OFF key, then release both keys.

    When initiating Diagnostic Mode, numbers may appear in the left display area with “EC” in the right display area. “EC” indicates the numbers at left are an “Error Code”

    If no error codes are registered, the left display area will show the real-time temperature of the thermistor being read, the right display area will show the thermistor location code, and all annunciators will illuminate on the LCD indicating the unit is in Diagnostic Mode.

    Pressing either COLDER key or either WARMER key while in Diagnostic Mode will toggle to the next or previous thermistor location, respectively.
    Click image for larger version. 

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    OWNER RICK'S APPLIANCE REPAIR
    APPLIANCE TECHNICIAN FOR 31 YEARS
    REFRIGERATION SPECIALIST
    ONLINE SERV TECH: ApplianceBlog.com
    CERTIFIED TYPE 1; TYPE 2.....REFRIGERATION SERVICE E.S.

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