Compressor start and defrost not working

[Chris D]

Hi,
I have a Liebherr CN 3813 20h 147 , service no: 0975044-08.

My first issue was that it didn’t appear to defrost, or if it did it wasn’t consistent.
Also, I could not find service manual, though the CN 3303 seems to be very close.

After unplugging defrost and measuring resistance it was about 420 Ohm (cf 400 for CN 3303), so seems alright. After further struggle got control panel off and measured resistances on 3 thermostats, one was warm, but on another measurement another time it was OK, so presume the defrost had warmed it. (2nd time I took steps to identify which was which).

Having now finally worked out how to get buttons to work sections manually, I turn power on to defrost and finding it definately wasnt heating up.
So I still thought a bit inconclusive, so on third occassion I tried to measure output from the defrost connector, but it only appeared to come through just under 6 Volts. I thought I was missing something (AND NEXT A BIG MISTAKE) .. I tried putting my meter to measure current … BANG.. big white spark from probe.. fortunately no harm, however now not sure what I may have done elsewhere (SO I NOW realise not to measure current without a load!).

However back to measuring Volts – still seemed the same (so maybe no harm done?) just under 6V, so conclude must be fault with control board. This time pull the board right out of plastic containers, and discover on the underneath of the circuit board a triac (0107NN) with part of its casing loose, and fell away when I touched it. Not sure if this was the original problem, or one I caused by trying to measure current, so have currently ordered replacement from Farnell.. However , now I discover the Compressor does not start automatically when put Fridge freezer plugged in as usual, back to automatic mode,I must have caused a new problem by the attempt to measure current. However the compressor will come on when I use the manual diagnostics? I am expecting my replacement triac alone will not now fix the problem (and will now at very least need a new control board), maybe a capacitor or some other electronic component has failed, but the parts are very tiny and there are no circuit diagrams to be found online, or maybe another part of the system is broken?
Any one with any further insights?
Thanks.

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