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rob clement
rob clement, Home Appliance Technician
Category: Appliance
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Experience:  20 years experiance working on all major brands of appliances
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My 20 yr. old sub zero 650 freezer temp is 32. Vacuumed condenser

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My 20 yr. old sub zero 650 freezer temp is 32. Vacuumed condenser coil not that dirty. Condenser coils slightly warm. Took suggested readings and got 32, 30, 14, -30, 00. What do you think is the problem?

rob clement :

If you look in the freezer do you see a buildup of ice?Is the fan running,you will need to make sure the fan switch behind the icemaker is closed.I suspect from your description and reading there may be a defrost issue.Can you check that out and reply back.Please keep in mind,I am not there and need your input to correctly diagnose your problem.

rob clement :

Hello,anyone there?

Customer: replied 3 years ago.

There is a slight crust of ice on the roof of the freezer. Something comes on when I remove the freezer door and then depress the 3 switches in back near the ice maker. The fan I guess? I am willing to expose the evaporator coils if you give me a quick tutorial. I guess I would remove the coverings on the roof of my freezer. My unit has freezer drawer below Fridge.

You should not have any ice on the freezer this point I would not take it apart just yet.Lets try and force a defrost.on the control,where you set the temps,press and hold the ice on/off for 15 seconds.At that point it should shut down and initiate a defrost.Let me know what happens.
Customer: replied 3 years ago.

I held it well beyond 15 secs. but it just alt between ice on & ice off. Should I get a confirmation that it entered defrost mode?


Also air temp inside freezer is 21 by multimeter with temp probe but display panel says 33


AND air temp in fridge compart. is 45 by probe but 37 on display?

Yes it should have shut off and went in to a defrost.Is there a service or vacumn condenser on the display?according to your readings from the control,the freezer thermistor reads 14 degrees and the evaporator thermistor reads -30.How is the fridge section,it appears to be ok
Customer: replied 3 years ago.

Yes. but I have vacuumed it x 2! did you see last edit on fridge temps?

I did see that post and it is not really a major problem as the control is sensing temps much slower and in different areas than you are.Is the condenser fan running and all gaskets look good.How did you get the readings from the control,by pressing a colder key and pressing on/off.If so can you do that again and check for error code before toggling between temps
Customer: replied 3 years ago.

Condenser fan runs well. Enough air movement to keep paper up against condenser coil. Yes, I followed your advice form a 3 year old post about obtaining the temp readings. Just say "vacuum condenser". Any other possible codes? Still have not been able to "force defrost"

No other codes,that should have given a fault if one was detected.When you try to force the defrost,will it shut down or keep on running,by running i mean is the fan on in the freezer and running or is it off.When you try to force a defrost what has to happen is the control shuts off the compressor,freezer fan,then send 120v to the heater system which is the heater and bi metal,or defrost terminator.Try the forced defrost again only this time hold for 10 seconds and listen for the relay click in the control.Then check to see if the fan in the freezer runs when you press the switch in the freezer.if the fan is off you should hear popping and cracking in freezer from the heater
Customer: replied 3 years ago.

It worked! Heard click and fan no longer running in freezer. Will listen for popping and thawing. Does defrost stay on when freezer open? Will let you know if returns to normal temps eventually. How long should defrost cycle last, ~1/2 hour? Have lots of kids (10) freezer drawer could have been left open for long stetches without me seeing it.

If the heater is working it will pop and crack pretty quickly,defrost will last +- 20 min or so.If it is frosted up that bad the forced defrost will not make it clear enough to work properly,it will take 2 days for it to clear all the ice.You will probably need to do that manually.Either by turning it off and leave open for 3 or 4 hours,or get in there with a hair dryer or heat gun to clear that ice.Let me know if you get any kind of defrost noises
Customer: replied 3 years ago.

Repeated forced defrost. Not hearing much cracking (a few unimpressive sounds, nothing at 2 minutes. Ice is melting on evaporator cover. If reg defrost with door open fixes it then I need a heater? If that works then I need a heater?

Not necessarily,IF that door was repeatedly left open or open for an extended period,defrosting it will fix the problem.The heater itself can't be bad or there would be no defrost,it either works or it doesn't.The defrost terminator "could" be bad but I don't change a lot of them.If you defrost it and 2 weeks go by and it is working,everything will be fine.As for pushing the forced defrost repeatedly,the control will only let you do that one time,then there is a dwell or down period it will not let you do it again.They don't want a fire or damage to the liner or wiring.
rob clement and other Appliance Specialists are ready to help you
just checking to see how the Sub Zero is doing and if there is anything else I can help you with.
Customer: replied 3 years ago.

All's well now. It seems the defrost was the cure. Temps returned to normal (0 in Freezer 37 in Fridge). good for the past week. Leaving Freezer drawer ajar seems likely cause. I enjoyed learning how my appliance works and I appreciate your "lets try this before you start taking things apart." approach!

Glad I could help.If you need help again just come on back.