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Steve Findlay

Sub Zero defrost troubleshooting

10 posts in this topic

Hi, I tried reviving an old post with a similar issue with no luck. Anyway, I'm having an ongoing issue with my freezer freezing up. Manual defrosts solve the issue only for it to return again in a few days. Last time I defrosted, I measured resistance on the heater element - it's not open, and I also put the terminator (the sensor on the cooling tube) in warm water and it audibly clicked.  Today the fan is making noise due to the encroaching ice build up, so I manually turned the defrost timer and after a few turns the compressor clicked off. I couldn't tell if the heater element came on since it's not apart but after about a coffee's time I heard the timer click back on - does this mean the timer is OK? I don't recall ever hearing this thing click on or off on its own... Logic tells me my next step is to take the cover off the top of the freezer, manually turn the defrost timer and physically feel the element for heat. If the element gets hot then start with a defrost timer? Does this make sense? 

 

Thanks in advance.

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Need appliance parts? Call 877-803-7957 now!

... I measured resistance on the heater element - it's not open,

... after about a coffee's time I heard the timer click back on 

... manually turn the defrost timer and physically feel the element for heat.

model number ?

1) should be about 21 OHMs

2) could be up to 25 minutes

3) should be able to see it glow

Edited by RegUS_PatOff
21 OHMs

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I set up the towels and turned off the freezer. I can't remember what reading I had before, I'll re-ohm it tonight and post back. Hopefully it's something easy like the timer or terminator. Thanks for the reply.

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Oh yeah it's a Sub Zero  Model 550  Serial 698245 built in '88....

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Post back with model NUMBER.


I guess we were typing same time.

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Defrost bi-metal should be closed when cold. Timer should be 21 minutes of defrost every eight hours of compressor run time. Check for 110v at bi-metal and heater while in defrost.

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You may have more of a drain problem than a defrost problem.  Check for blockage of the defrost drain to the right of the evaporator cover.  If found blocked you should be able to clear it using hot water and a turkey baster.  Newer model 550's had a defrost drain heater kit but this kit doesn't apply to your serial number range.

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These cal-rod heaters seldom fail, nor do terminators, if it's the original defrost timer, I'd replace it, they can stall out at times. If the drain tube is freezing up, since your unit has a drain tube too small to fish a heater through, feed a piece of copper wire as far down the drain as you can and wrap the other end around the defrost element, not a perfect fix, bit it beats a blank.

Sent from my SCH-I545 using Tapatalk 2

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Update: heater element reads 20 ohms. I put the terminator in our 2nd freezer and the circuit closed after a few minutes so it's good. I manually put the timer in defrost (while the terminator was still closed) and the element turned on. I picked up a defrost timer (8hr 21minutes) on the way home from work. It's for a Fridgidaire but looks identical; terminals match. I can see the gears turning but don't think it's working still. I'll keep an ear out for it and if I don't hear it over the next day or two I'll swap in the new one.  Thanks again for the input.

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Update: I swapped in the defrost timer and it has been working like a champ ever since. Ice cream is rock solid and ice cubes are dropping like clockwork.

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