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I need some sub zero help - Sub Zero 550 that is warm in the fridge section


Premium Member
Nov 13, 2022
Ansonia, CT
Model Number
More than 10 years
Good morning! We have a sub zero 550 that is warm in the fridge section. The freezer is at around 20 degrees and holding. The freezer knob is set to #4. The fridge is at 62 degrees and we cannot get it to cool down. It was recently moved, and has not cooled down after letting it sit for over 3 days powered off. We have replaced the dual sensor refrigerator control, part # 4201260 thinking that could be the problem. However, since starting it about 22 hours ago, it is still at 61 degrees. I have tested the fan in the fridge by opening the door and pushing the light buttons to mimic the door being closed and the fan runs. The only other thing that I do hear is that every little while, I hear a humming noise that gets a little louder for all of 5 seconds. Like something is trying to run but can't. Does anyone have a clue to our issue? The condenser is clean, and I can hear the unit running smoothly other than that hum that happens. The walls of the fridge seem like they are getting cooler, but I think it's my mind WANTING it to be cooling. Thermometer says 61 right now. We have not tried to re charge with freon. Is that something a tech should do or can it be done by the user?
Serial #? Freezer should be Zero or below. The hum is compressor trying to start, you can put your hand on it to feel it. The one on the right. No sense trying to recharge if compressor is shot, a tech or you has to put gauges on it to see what's going on. Moving it shouldn't cause a comp. failure.
here is the fridge info. It sounds like the compressor is running, but there is the additional hum. I just re-checked the freezer temp. It was at -2 degrees. Thank you for your thoughts, as I am growing frustrated by the day.


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It worked before moving? Are you original owner? Cannot really tell by sound since there's 2 compressors plus fan running. Shut off frz & unplug fan & put your hand on top of ref compressor. Someone needs to put gauges on comp. Pressure should not be below 6lbs psi if running.
I am not the original owner. Ours died, bought this from someone else who said it worked fine. hahaha. I think we are stuck with another dud. Good thing is that we only paid 600 bucks for it. Well...and the new part. I think we're gonna call it a day, I don't think we are gonna invest any more $$ in it. Just as an inquiry, if it IS the compressor, what are we looking at for $$$? I am so very disappointed though. Now we have to search for a fridge that will fit our cabinetry without spending 13k. Thank you for your help.
When you installed the new control were you able to crimp the one cap tube to the outside of the evap or behind the evap, not the tube with the bulb on the end. If it needs a compressor and still has the old evap in it I never do the job without replacing comp, evap, heat exchanger & control. Cost is $2150.00 and most do the repair considering the cost new. I always go by cosmetics, if still pristine after 25 years it's worth it. You can call SZ on the # on that tag and ask for a service history on the unit.
Hello again. I did as you advised and turned the freezer to off, left the fridge running. The loud humming has stopped, and the fridge is now at 55 degrees. I would love to try and save this unit, as we are only going to be in this house for another couple years. I just can't see buying new just to leave it here. I have contacted the party that sold it to us, not holding out any hope there. Both tubes are behind the evaporater. Do you mean the little 3-4" piece that extends from the bulb? The fridge is a very nice, clean unit. We have to switch out the panels for ours, but we will wait and see if we can get this one going. I truly appreciate your help. I am also going out to find a new thermometer. I think the one I have isn't working correctly, although the fridge is clearly too warm.
Since the tubes are behind the evap it has been upgraded because of a freon leak( plus I expanded your tag pic and saw the new freon amount sticker) That's a good thing. Since it's close to 25 years old I would shine a flashlight thru condenser right to left and see if it shines thru. Also ask seller how extensive the evap replacement was and who did it. I meant to ask, you have one now? What's wrong with it?
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Will do. Thank you for your help today. I appreciate your advise on a Sunday. We are not in an emergency mode, as we have a smaller fridge for the time being. Do you service sub zero's? I am in CT, if you are not able, can you refer a service tech that does? We have used a couple over the years since we bought our original 550 in 1999. The techs we have used always try and sell us a new one. Thank you again for your help today. I'll get back to you as soon as I get the service info.
That & Wolf are all I work on, but you're too far away. Go to their web site and put in your zip code. Your old one is newer than the one you bought, what was wrong with it?
That & Wolf are all I work on, but you're too far away. Go to their web site and put in your zip code. Your old one is newer than the one you bought, what was wrong with it?
same thing..warm fridge, ice bergs under the crispers, drain tube was cracked. Door hinges were broken, rust everywhere because of the icebergs, our wood panels were turning black from the excess moisture in the doors. The current fridge is pristine, only has the warm fridge issue. Every tech we brought in said it wasn't worth fixing. I didn't believe them, but what do you do when you call sub zero, the same techs are the ones that only want to sell you a new one? We THOUGHT, because we were told, that this one worked and could hold us over for a year or two. I have spoken to the seller, but as you probably have guessed, they have washed their hands of the situation. I wish I could find someone that was interested in fixing this.

I have a quick quesiton. When you asked me to turn off the freezer, but leave the fridge running (that's when the buzzing stopped), what was that for? What does that show us with regard to what is not functioning. Oh...and the original tubes (not sure if I misunderstood) for the evaporater were behind it, but did show signs that it had been previously worked on...and not to well, if I may add that. I will see if I can get the repair history today. There is a group of sub zero techs out of NJ that supposedly service our area. Certified Refrigeration...do you know of them?
I'm not familiar with them but their web site is good. They might have been L&J once upon a time and if so they are good. Without hearing the buzz it's difficult. If you could download the sound it would help. Why do you say not to well? Pics?
That & Wolf are all I work on, but you're too far away. Go to their web site and put in your zip code. Your old one is newer than the one you bought, what was wrong with it?
You sure you are too far??? Only a couple hours...we'll pay for gas and travel time. Can you tell we are desperate for a good tech? Just a messy job once you took the back panel off, the tubes were just kinda hanging there, not really crimped or secured. May be the standard, but husband is quite particular about his work. I just turned the freezer back on to see if I can record the buzz. It will probably take a while for it to cool down again.
Are you or hubby competent with volt meter, so far it's just observations and this is really a simple diagnosis after basics are checked. I'd like to make this as simple as possible
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