Slowly dying freezer - advice sought on approach

[Dusxpress]

I am a new member here and hope this post makes sense:

It is related to a home appliance, a combination unit Miele KF 7562 S.

This unit was purchased new in Dec 2000. It never had any problem in its life, and was almost never switched off. This is the unit with 2 compressors and an electronic board with displays above the door.

The upper part now still works fine.

The freezer part does not work.

It slowly ceased to work, showing the temperature on the display lower through time (-13, -9 within 2 weeks, now no minus (it still gets cold inside) - We have kept it at -20 as standard all these years, we are the 1st owners and the unit was never in problem or repaired. It was well maintained in terms of defrosting).

When only the freezer is switched on, the compressor starts, the display works, temperature can be selected etc, beeper works.

I can send a small video that will show the sounds from the freezer compartment if that can be useful? (After freezer boxes were removed I recorded a video after switching the freezer on: a (not loud) humming noise, changing in sound / frequency, sometimes like a water is flowing etc. is to be heard, sometimes a louder hum etc. inside the freezer compartment.)

I suspect that the compressor is bad or the gas has leaked?

On recommendation from someone, we had a refridgerator repairman having a brief look 3 weeks ago: they only measured temperature in both compartments, and it looked as the minus in the freezer part, of the freezing boards directly - (I suspect the infrared measurement took that data somehow from the surface of those boards) - was very low - minus 30 (while the display was showing - 12).

That repairman made the following diagnosis: that the electronic board above the doors was not good, that the compressor was working constantly until it won't be shut off by its own temperature sensor to prevent damage to the motor, and that it is not worth repairing because the electronic board is way too expensive to replace and everything is already old and not energy efficient. He estimated it may still work like it was working for few more weeks, and then it will die. In the coming weeks it indeed ceased to produce minus slowly, to the present situation that is as described: it produces cold on the boards in the freezer parts, but it does not create a minus at all...

I do not understand how the electronic board can control work of the compressor to the effect that it can adjust the temperature other than just switching the compressor on and off based on the selection of the temperature and information from the temperature sensor.

Does it make sense to do another checkup, possibly replace the compressor and/or add gas in this freezing circuit? When asking here so far nobody seems to be interested to repair such an old appliance... Miele service is a rip-off, probably will end up with the same recommendation - buy new Miele (visit and 20 min work for diagnostics is 125 EUR, anything else plus).

One more information that goes along with that measurement of very low temperature by a repairman: on one occasion, while the display was showing -12 / -13 , when I opened the freezer door, it produced a lot of cold steam, and indeed it looked as everything in that freezer was way colder than -20, which was our normal. I switched the freezer off then, and after few hours switched it on - that "very cold situation" was never spotted again (this was mentioned to that repairman, could have influenced his conclusion and final assessment?). We kept the unit on, occasionally switching it off manually, until all food that was inside was used. Approximately at the same time it stopped showing a minus...

Would this information be useful for making an advice what to do with this appliance? Should it indeed be just thrown away? Thanks in advance for any suggestion.

[frank]

If you put a glass of water in the freezer do you get ice?

Do you have a seperate thermometer handy to take temperature readings?

[Dusxpress]

No, it won't produce ice any more. It gets cold similar to the regular fridge, I believe +4 / +5 degrees now. It was slowly going down from -20, for few days -17, then -13, then -9 etc till it stopped showing minus on its own digital display (so I think internal thermometer and control board are fine).
I'll check what is happening now, need to move it towards the middle of the kitchen (risking to be killed by others here who would only like a new one to be purchased...). I think if switched on, the motor works constantly. While it was working in this dying mode, never reaching the minus that was setup by the control board, the freezer compressor would be significantly warmer than the fridge compressor next to it, but still it could be touched without burning you hand...

[redroge]

Lost it’s gas at that age time for a new one !

[Rob White]

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A few options.

No1
The system is either losing refrigerant or the compressor is failing and that is showing over a few weeks. Quite a common fault. Compressors are replaceable and leaks are repairable but for something that is 21 years old not really viable.

No2
The system is iced up and failed over a 2 or 3 week period. Defrost for 48hrs and test. Cheap easy fix.

No3
The controller has a probe sensor fault that is displaying the wrong temperature. Quite a common fault but due to the nature of the controller not necessarily an easy fix.

No4
The controller is faulty. Expensive to replace and the fridge is still 21 years old.

You need to weigh up how much this 21 year old fridge is worth to you.
You could throw a lot of money at it ant still have a 21 year old fridge.

No easy solution without have a proper look at it?

Rob

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[RANGER1]

Just to add to Rob's & others good advice.

Door seal not sealing, should feel resistance when opening door.
This can cause major issues, like Rob says iced up evaporator, need extended defrost.
If it has a fan in freezer, is it working.

Other general, but nothing to do with issue is clean condenser, if has fan cooled especially, as gathers rubbish on coil face.

[Dusxpress]

Thanks all. You are probably right re age and danger of throwing money in repair. On the other hand, I would like to know what has happened especially as that mechanic said it is the control board that caused the problem, and now I am sure that is not correct. I'll see about the cost for new compressor and if it is meaningful to try to repair.

Not sure if this can put more light: When the freezer is turned on, just a weak sound is heard from the freezer in that moment (listening carefully just next with my ear to the cooling board inside the freezer - door is open, nothing is in the freezer. After 1 min or so, a more louder sound happened, like if some pressure has been developing inside, and at one moment that pressure is relieved, and the gas flowing at higher speed inside... That lasts 5-10 sec, and then it continues with less noise... Compressor gains very little temperature after 1 hr, and the cooling effect inside is very low. So it is either too little gas, or weak compressor.

[Rob White]

Thanks all. You are probably right re age and danger of throwing money in repair.

Snip

Compressor gains very little temperature after 1 hr, and the cooling effect inside is very low. So it is either too little gas, or weak compressor.

I can't answer for certain without fitting a set of gauges but your
observations are very informed and are the most sensible option available.

Rob

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[frank]

With the compressor running for over an hour and not getting hot, I would rule out loss of gas. More like inefficient compression due to wear and tear.

[skarrs71]

Check your temperature readings! A second thermometer to compare to the display.