weak cooling – Miele tall freezer

[Stub43]

Model Miele FN 4893 S
When we returned from summer holidays the freezer temperature was flashing at -10. Restarting and leaving unplugged for 24 hours did nothing. A week or so later it was at -8 and this continued until it got to -2 by which time we’d eaten all the food and switched it off.
Weeks later I’ve switched it back on but it took 24 hours to get from room temperature (+14) to -7 using Supercool and in an additional 12 hours it has maintained -7 but not got any cooler.
The freezer is in a garage so doesn’t get too hot, even though it was a hot summer, but this year some cardboard boxes were piled up against it, so ventilation was reduced.
At the time I noticed a few drops of bright blue watery liquid on the copper pipes at the back and some residue at a couple of joints where it looked like liquid had evaporated at some point. There has been no sign of any liquid since.
There have not been any fault codes displayed at any time. The seals are all fine.
Can you help me diagnose the most likely fault?
Thanks very much, Stu.

[admin]

Re: weak cooling – Miele tall freezer

Evaporator sensor not turning the fan on ?

Bryan

[Stub43]

Re: weak cooling – Miele tall freezer

Thanks for responding. I’ve just checked and I think the fan is working as when I open the door, the noise subsides to a much lower level. When I close the door again, there is a very fast hissing noise that sounds like it could be a fan pushing air very quickly at high revs, then after 5-10 seconds it slows down to a more rumbling sort of level. Does that make sense?

[spimps]

Re: weak cooling – Miele tall freezer

If there is any sign of frost on the inner back panel if so you could have a an ice build up on the evaporate blocking the air circulation.
Empty and turn off for 48 hours with door open to allow to clear, might be a sensor at fault so if it occurs again after a few weeks you would perhaps need an engineer.

[Stub43]

Re: weak cooling – Miele tall freezer

No sign of frost/ice and I’d already tried a couple of times leaving it for a few days then restarting.
From the description in my last post, am I right in assuming that the fan must be working OK?

[spimps]

Re: weak cooling – Miele tall freezer

If everything is running ie fan and compressor then it would likely be a system fault if it’s not getting down to temp.
When opening door you can usually hear fan shutting down.
Is the compressor/motor very hot to the touch,and running constantly if it is another possibility is a slight refrigerant leak which could show these symptoms also maybe compressor could be faulty.
It would need an engineer with the appropriate equipment to correctly diagnose the fault.

[spimps]

Re: weak cooling – Miele tall freezer

The hissing noise by the way is usually the air pressure equalising between cabinet and outside after closing the door.
Could be the fan sensor too as they don’t usually start the fan up until the sensor which is on the evaporator is around -12c.
I have a miele upright and can distinctly hear the fan slow down as the door opens.

[Stub43]

Re: weak cooling – Miele tall freezer

That’s very helpful, many thanks. The fan sounds quite rumbly rather than free-spinning when I put my ear up to the side of the freezer. I can hear the fan stop, though it stops quite suddenly.
The compressor is running constantly and is warm but I wouldn’t say very hot to the touch as I can hold my hand on it.
Is this significant?

Also, does it help to look at the problem from another angle, i.e. what might have caused the fault? – if it did overheat in the summer because the ventilation was restricted at the back like I described in my original post, what damage might that have caused?

[Author]

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