SubZero 550- Question about freezer icing over

[Oldsalt]

Original owner here S/N P1038850. For a while I have been battling the freezer evaporator coil freezing over. It’s time to finally fix it. Soon after I got the unit a service man came out and put a heater coil in the drain tube under warranty. I can’t recall exactly why. If that drain heater has gone bad would that cause the evaporator coil to ice up or is it something else? What is the fix?

The freezer has been shut off (Drawer propped open) for about 2 months now. I got called out of state for a bit so I just shut it off while I was gone.

Second problem I just noticed, the back wall of the fridge is icing over starting in the lower left area. First time this has happened. Fridge drain seems clear but I haven’t really checked. There is no ice under the crisper. What is happening and what is the fix?

Aside from these two things and the fridge drain freezing once years ago this refrigerator has worked flawlessly for all these years. Even when the freezer evaporator coil ices over it still keeps everything frozen.

I’m going to replace the ice maker as well but that is pretty cut and dry. The paint is flaking off of the ice molds.

Any help, advice, tips or part numbers is greatly appreciated.

Thanks in advance
Joe

[Hiroshi]

The refrigerator forming a frosty patch at the lower left is a telltale sign of a refrigerant leak. A few ounces of refrigerant into the service valve should fix that.

The freezer evaporator icing over is a defrost failure- first locate the defrost timer, should be mounted behind the access panel on top where the compressors and condenser are, more specifically, mounted on the bulkhead between the compressors and condenser coil... take a flat blade screw driver and rotate the barrel with the notch in it on the defrost timer until it makes a decisive "click." The freezer compressor should cycle off- this means you have manually entered a defrost cycle. After a few minutes, you can open the freezer and see if you can detect melting/thawing and/or heat coming from the defrost heater mounted below the evaporator- If there is heat and it is defrosting: replace the timer. If there is no heat/ no defrosting going on after ten minutes, it's time to open the evaporator cover and check the defrost thermostat! 

Part number: W10822278 = defrost timer

Part number: 12001937 = defrost thermostat

[Oldsalt]

Thank you for the reply Hiroshi.

I have the freezer disassembled (cover off etc.) at the moment and the freezer has been shut down for a while. Given that, I might as well just replace the timer and thermostat and be done with it. The parts are cheap. Two questions though- 1) Is it possible the defrost heater is bad as well and not just the timer and thermostat? and 2) The parts you listed in your reply are Whirpool parts, are these interchangeable with the Sub-Zero?

Frost on lower left of fridge- I’m going to assume that the leak is in the evaporator coil. Since I don’t have a leak detector or the equipment to recharge the system I suppose my only option is to have a tech come out and replace the evaporator. I can prepare everything before he arrives. I don’t mind investing in buying tools/equipment but for what would really be a one time use it’s just not worth it. Also from what research I have done, topping off the refrigerant is a temporary fix.

While I’m at it should I also look into installing the Sub-Zero ‘floor defrost package’?

A couple weeks ago when I first noticed the frost/ice in the fridge. I shut things down and defrosted at that time. At this time the ice is back again. The compressors do seem to be working a lot but the fridge is keeping cool. Am I looking at a bigger problem if I don’t get this repaired soon (within the next couple weeks)?

Thank you again for your advice.

 

[johntech]

yes, there is a much greater chance that either the heater or  bimetal thermostat is bad. That is why hiroshi suggested you turn the timer till it's in defrost mode so that way you can get an idea what is going on in the defrost system. You will need to have the unit running for 24 hours so that the defrost bimetal will be cold enough to allow power to get to the heater or you will not get accurate results. 

[Oldsalt]

Thanks johntech. I've got the covers and such off but I will turn it on for testing. You think it will be OK empty or should I fill the freezer with some water bottles?

Any comment / advice on my other issue?

Thanks

[Hiroshi]

It's fine if it is empty. The whirlpool parts listed will work great on sub-zero machines (sub-zero doesn't manufacture their own version of these parts anyway), but the images are more for illustrative purposes to help in your diagnosis... The cal-rod style heaters on these units rarely go bad themselves, I have seen it happen, but it is unlikely.

As far as the evaporator leak goes, I would contact Sub-Zero and give them your serial number- They are great when it comes to their warranty, and I have known them to extend customer's warranties for free, simply to ensure you use a factory approved servicer for the evaporator repair...(which means free parts!) so, that is worth a shot.

Topping off the refrigerant is only temporary in relation to how quickly the gas is escaping, it may take years for it to leak a significant amount, but if I were you I would also get it repaired the right way A.S.A.P. (especially if Sub-Zero will spring for the parts)

[Oldsalt]

Great! Thanks Hiroshi.

Got the freezer up and running yesterday afternoon and will do your defrost timer tests today.

Don't know about Sub-Zero honoring a warranty as the fridge was bought and installed in '94

but I will give it a shot.

 

[Al Chisholm]

I have a circa 1994 550 with exactly the same problem. After reading up on it here and doing a few hours of work I think I found the cause (at least in my case). There is a metal strap that is wrapped around the defrost heater element and extends down the drain tube in the upper right wall of the freezer to prevent ice blocking the drain tube. Its behind the drain pan and getting to it is a minor pain. It turns out the strap only extended about an inch down the tube where it was all mashed up into a little accordion shape. I'm surprised it worked at all... Rather than trying to straighten and reinsert it I pushed about 10 inches of copper wire down the tube (neutral wire from some 14 gauge romex) and wrapped the end around the heater about 3 times (also easier said than done). We will see how this works out... I vaguely recall that a repairman might have replaced the evaporator core in the freezer soon after I bought it. I'm guessing he was the one who mashed up the heater strap when he put everything back together.

[TheAlchemist]

So I had this same exact issue with my freezer not going through the defrost cycle.  I ordered the new timer, but received one with the wire lead on it, which I've come to discover needs to go over the correct terminal in order for it to work.  I have the wiring diagram, but as the name implies, I'm a chemist, not an electrician, and reading wiring diagrams isn't my strong suit.

 

Can someone advise which terminal the lead should go over?

 

Thank you.