Miele KDN12823S iced up evaparator

[lewisham_phil]

Hi; I’d be grateful for a bit of advice on a plan of attack on my Miele (KDN12823S Nr. 21/96559014 Index 20F 164)
It has worked fine for seven years, but has been slowly warming up over the last week or two. (fridge now up to ambient, freezer at -5 to -8; the alarm finally sounded today).
Following advice here, I am currently defrosting the rather solid mass of ice on the evaporator. I shall investigate further tomorrow.
First question; is it definite that something is wrong, or could it be that the ice has slowly built up over months or even years? I’m not sure how the defrost is controlled to know that all the ice is clear..
So should I run it as normal and see if the fault recurs?
If something is wrong, what is the most likely cause on a ‘Frost Free’ Miele (Liebherr) of it frosting up?
Thanks!
Phil

[lewisham_phil]

Re: Miele KDN12823S iced up evaparator

Right, fully defrosted overnight, and it’s cooling down fine, freezer circulation fan on, down to -18C, and the fridge is also cooling down. All looking good. I just want to monitor it a day or two before I replace the evaporator cover panel.. I want to see if it defrosts OK (which I realise might be affected by not having the cover panel in..) but I wonder if anyone can tell me the frequency and/or trigger for defrosting on the Miele.. is it timed? And what controls the duration of the defrost cycle?

[Tony R]

Re: Miele KDN12823S iced up evaparator

Defrosting: ON: – During start-up after 6 hours cumulative compressor running time. – After a cumulative compressor running time of 6 to 60 hours maximum, depending on the number/duration of the door openings.
Regards,
Tony.

[lewisham_phil]

Re: Miele KDN12823S iced up evaparator

Thanks Tony: do you know what controls the duration of a defrost? I’m trying to determine possible reasons for it icing up.
I’m sure the heater is working as I caught it in mid-defrost earlier, with molten ice dropping into the drain gulley. So it’s either a sensor, or the defrost not quite defrosting, allowing an incremental build-up. Is there a sensor within the evaporator? There is one mounted on the front of the evaporator cover panel, but I can’t imagine that can give any useful feedback to determine whether it is fully defrosted.

[Tony R]

Re: Miele KDN12823S iced up evaparator

There is a sensor inserted into the bottom of the freezer coil, this sensor determines the end of the defrost cycle and the operation of fan.
Defrost is controlled by the integral board as my previous comment.
I would say that this is more than likely where your problem lies.
Changing the sensor is your best route.

[lewisham_phil]

Re: Miele KDN12823S iced up evaparator

The bottom of the evaporator coil makes sense, where that big solid lump of ice was blocking any air! I have emailed the spares department for the correct thermistor part number.
Thanks again for your help.

[lewisham_phil]

Re: Miele KDN12823S iced up evaparator

Just had a word with the spares department, who have kindly sent through an exploded diagram: It’s not 100{e5d1b7155a01ef1f3b9c9968eaba33524ee81600d00d4be2b4d93ac2e58cec2d} clear, so I wondered if you, or anyone, had a definitive part id for the defrost sensor I need? And finally, a basic note of how to get at the sensor; I assume the white foam rectangular pad (is that the defrost heater?) behind the evaporator cover panel needs to be removed?
Thanks in advance!

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