Whirlpool SB540W American Style Fridge Freezer not cooling?

Hi Board!

Can anyone help please? I have a problem with a Whirlpool Fridge Freezer Model No: SB540W large American style, Serial Number: 8586 411 15010.

Everything powers up fine with lights etc and the Fridge and Freezer cools but not down to the required temperature – hence my question.

The compressor runs – at least it sounds like it’s running – and the Fridge cools down to 2 degrees but the freezer only cools down to -5 degrees. The external digital read out states -18 on the control panel which is obviously incorrect. The fridge is quite noisy – I assume the compressor is running constantly as its trying to cool the freezer but not succeeding.

Having removed the lower front cover and thoroughly cleaned out the all the underside grills etc – which was full of fluff, I removed the rear internal panel inside the freezer to check the connections and fan was ok. The fan was running fine but one of the sensors had come off of the internal pipe – which I clipped back on. You can see this at the top of the photo attached. I guess what will be more obvious to most is the lack of frost across the entire unit itself? Although not being very knowledgable I’m assuming should show constant frost across the entire tubing? This is as icy as it seems to get over about 48hrs – which I assume is the problem?

Is it possible for anyone to suggest from looking at the photo of the non-frosty (technical term! Ha Ha) what I should try and look at next from a diagnosis point of view ❓

Thanks in advance for any help anyone is able to supply.