Bosch KGU2312121GB Misbehaving

[RichLion]

Hi there, if someone can advise I would be grateful!

I have a pretty old Bosch KGU 23121GB which although being quite noisy with a rattling sort of sound, has been pretty good.I do not have the manual.
a few weeks ago, the alarm started going off,and the ice wasn’t melted in the top tray of the freezer compartment. Fridge seems ok.
I had a look (broke the tabs!) taking off the back panel, and it was fairly icy, For one, I think the fan was gone(240v across it-no spinning) bought a pretty pricey replacement(EM2513LN-198), which said it was the right part on the site, but had a different plug, so sorted that out( not very pretty but..). After testing and checking against similar problems/ models from this site and elsewhere, something else must be wrong.

The freezer reaches -18 again, after some time and I have noticed( and the alarm has gone off again!) it going to -5 sometimes, then after a few hours, back to -18? Surely if it freezes stuff its not the gas that is the problem?
It can’t be defrosting every night surely, nor need it straight after finishing the work(all defrosted) there seems to be a bit of buildup, but I don’t know how much before it really affects it?
It is doing this cycle every night now it seems, not always the alarm since I did tinker with the defrost cycle setting like in this post below, I am guessing the control board works?
posthttp://www.ukwhitegoods.co.uk/forum … t4666.html i think it works on mine and I tried changing it. The other ‘settings’ seem to also tell me inside and outside,fridge temps etc it seems, there seem to be 9 (+2) ‘options’ that only 2 (programme 10 &11?)seem to actually do anything, they seemed to work as in the above post.

It mostly has always operated with lots of gurgling,rattling sort of noise and on quite a lot( i haven’t tested current draw). By ear the rattling,seems to come from the top fridge.It goes quiet for a while as the temp drops ..Sometimes it seems if i switch off and on it makes a different noise, you hear a plink, and it seems to gurgle back to -18, sometimes not. My friend re-tested the fan at work, as it wasn’t spinning but seemed to be 120v on the terminals? But he checked it fine and is more experienced than me, so I refitted it and assume thats not the problem.

In the mornings its mostly near enough reading -18 again)
Recently the top drawer seems to be frozen (mostly again)but so far I still can’t bring myself to trust meat in it..

I have I think the bottom connections seem to be similar to this post but with another 2 connectors on top:
viewtopic.php?f=35&t=60815

Top 2:

Red surround(grey plug) – possibly ntc sensor?
white surround plug – fan

Lower 4:

white plug(black wire) -thermal fuse( seemed to test ok for continuity)
grey plug- defrost drip tray heater(tested 1200 ohms, although possibly should be 2700 ohms?)
black plug- heater for evap unit ?( tested 300 ohms)
red plug -defrost heater? (cant recall test, but temp goes up so fast surely not?)

Its a bit tatty, however does the job,,but if its really just wasting energy(B rated), it was second hand, certainly not worth any big parts/ gassing.The main fan (if thats the rattle seemingly from the fridge) is about £90! The only part I feel I have not tested is the NTC(?) in the little white box thats seems hard to open. Could that be the culprit( and the plinking noise)?:
http://www.buyspares.co.uk/fridge-freez … ef=2946278

If anyone can advise it would be grand, its driving me mad.Just waiting to hear the different odd noises..Clicks, pumping sounds, like its thinking, oh and creaking a bit more(since i broke the panel lugs!).A similar replacement is pretty pricey with auto defrost, led controls for temp and decent( ish) quality.
Sorry for the long post.

thanks in advance!

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