Liebherr Fridge Freezer KGT 3456 not working

[CG2]

To be a bit more specific, I've got a 20-ish year old Liebherr that has just stopped working. This was quite a sophisticated beast for its time. It's a twin compressor model, and you set the desired temperatures of the fridge and freezer parts from a couple of little control panels above the door. It displays the actual temps on some eight segment displays there, flashing if it's working to get to where you want it. There's a control board with a microprocessor on it that read the temperature from a couple of sensors, switches the compressors on as necessary, and runs the display. There's also a Supercool button if you want an extra boost. I think that this is a timed boost unrelated to actual temp. After all, the compressor has only one speed.

Now the fridge has just stopped working. It's displaying 11, which seems to be the highest temp you can set the fridge (clearly the designer was a Spinal Tap fan), and if I try to adjust it, it flicks straight back to 11. If however I press the supercool button, the compressor starts up, the back of the fridge gets cold, and the number on the display changes to reflect the actual internal temperature.

I checked the motor capacitor on my meter and it is showing 2.46uF, against a spec value of 2.5. Probably better than any new one I could get. The start up relay looks fine (it's one of those little round ceramic discs), and both must be working because I can force the compressor to start. The temp sensor seems to be working because the display reports the actual temp when I've got the supercool button on. I've had the PCB out, everything looks OK, no bulged capacitors or burnt resistors. No fault codes are showing. If there was a leak then surely the compressor would not work at all. I don't think the overheat sensor sends any feedback to the MCU.

I suspect that it's not fixable, but even so my pride is hurt. I don't like throwing stuff out without knowing for sure how and why it broke. Does anyone have any thoughts?

[stj]

if it has up and down buttons, suspect the up button is shorted or contaminated.

[redwire]

There's nothing on that model "KGT 3456", no manual or service info. Other variants ECPc 3456 or ECc but little but a few spare parts.

There are a few temperature sensors, I would check what they are reading with a multimeter. It might think the evaporator temp is out to lunch but it has error codes F0-F9 which supposedly cover them. ie. Liebherr 9590206 temperature sensor 4.7kΩ@+25°C, 3.1kΩ@+35°C, 11.9kΩ@+5°C, 15.3kΩ@0°C, 45kΩ@-20°C

Or the settings are scrambled in it.

[CG2]

Originally Posted by stj

if it has up and down buttons, suspect the up button is shorted or contaminated.

Genius. I was so convinced there was a big fault that I overlooked the little things. Especially as I've not touched that button ever. The fridge arrived set at 5 degrees and there it's stayed. And it had also begun to give some very short cheeps from the speaker, suggesting that the processor was registering some very brief button presses. I turned it off and pressed the up button 20-30 times, and that seems to have cleared it. I hope that works since it looks an absolute pig to get to that part of the circuit board. I snapped a couple of fragile clips getting the horizontal mounted main pcb out that was in front of it. That was connected to the display panel board by the stiffest "ribbon cable" I've ever come across, which in turn was held in by lots of hard plastic clips in a casvity 2 inches wide and 2 inched deep. Rock solid build quality, but not designed to be taken apart.

And a slight correction, I had a dyslexic moment and called it a 3456. It's actually a model KGT 3546. Apologies. It dates from an age when error codes only went to F5.

[stj]

button contamination used to be common on tv panels

[redwire]

I guess it's moisture in the keypad? Quite a few complaints about Liebherr refrigerators- counter to OP's running 20+ years. They are hard to design, condensation, trays breaking etc. nowadays the compressors don't last.

[CG2]

Even when this fridge was made, Liebherr were sourcing compressors from outside. The freezer circuit uses an Embraco EMU32CLC, and the fridge an Aspera BPK1058Y. A quick Google tells me loads of fridge companies use these. I guess the compressor companies are cutting corners as much as everyone else nowadays, and the drop in quality is working its way down the line. I'd never thought to choose a fridge based on the compressor used, and I wouldn't know a good one from a bad one.

That does make me wonder what is the difference between different brands if they all source components from the same place. I was wary of glass shelves, but they've survived fine. I guess those are made by the glass company and brought in finished to Liebherr.

Elsewhere, the PCB itself looks well laid out, the soldering is clean, and the relays are good quality ones.

The clever door opening mechanism that relied on a little bit of plastic remining flexible gave up a few years back, but that means that rather than pulling up the handle to press a little button against the fridge body, you just pull on it to open the door. I think that handle design got binned years ago. The doors still open and close cleanly.

I reckon I've got my money's worth out of this one.

[stj]

why do you need a mechanism to open the door?
the temperature differential sucks the door shut anyway.
i have 2 fridges and a freezer - none have latches on them

[redwire]

The latch might be some kid safety thing?

My Whirlpool fridge door won't open due to the vacuum, you have to yank hard or peel the corner of the seal to get it to open easy. Grrrr.

[CG2]

It's not really a latch, nor a safety mechanism, just a stupid bit of over-engineering that's a bit hard to describe. There's one part of the handle that is fixed, and comes straight out like a normal fridge handle. Then there's another part attached to it that is hinged on that part and sits parallel to the fridge front. One side is the bit you pull, then there's the hinge, and finally a little plunger. When you pull on handle, you're operating a lever which pushes the plunger against the main body of the fridge and thus pushes the door open. I assume the leverage gave some mechanical advantage and made it easier to break the seal when opening the door. You flip the long end of the handle 3-4 cm, and the plunger goes down 1/2 a cm or so. The plunger bit is slightly springy, and that springiness is meant to come from flexibility in the plastic. Over time it loses that flexibility and breaks, then you end up pulling on the handle to directly open the door, just like on every other fridge. I had a look for a replacement once. They had abandoned that design, and wanted over £30 for a simple handle, so I let it be.

I've found a video. It's only 9 seconds long too. https://www.youtube.com/watch?v=2uwwlwhCNNA

And if you want to see what's inside https://www.youtube.com/watch?v=VsmKz3yh6SE

(I seem to be going down a rabbit hole of fridge opening mechanisms) Liebherr have quite a thing for over-engineering doors. Their latest works via alexa or via knocking on it. https://www.youtube.com/watch?v=a9Yq9NT_sRY

[sam_sam_sam]

Embraco Compressor are not the best compressors in the world either they are noisy or they fail prematurely this has been going on for years so who knows what there quality is now I replaced a lot of them on ice boxes for a ice company many years ago this was on their small ice boxes that use these compressors

[redwire]

Loads of Embraco compressors are made in china. These appliance conglomerates source parts all over the world and compressors are out of Korea or china and with new refrigerants or cornball mechanicals to score higher efficiency, they don't last. Example LG linear compressor is shit, second class-action lawsuit. New stuff isn't better.