Problems with Samsung Fridge/Freezer (fridge warm) SRL3616B

I have a Samsung Fridge/Freezer. Sorry for the long post but I want to include all the details in case they are useful.

The Fridge stopped cooling last week (Freezer temperature was fine). The
compressor was not running often. I have looked at the FAQs and done the following:

Emptied and switched off for 24 hours. I removed the panels around the evaporater. There was a small amount of ice at the bottom.

I waited until it had fully thawed and dried out. Then I switched on the appliance breifly and observed that the fan was running and the fridge flap opened and closed when I operated the door switch.

I checked the resistance of the fridge thermostat and that was 6K at 20C
as per the manual.

I reassembled the appliance and left it switched on overnight with only a few items in it. In the morning the fridge is 5C and the freezer -18C!

However the compressor seems to be running all the time (I am not in the room continuously). The fridge/freezer doors have not been opened much today and not at all for at least 2 hours.

One other fact is that the door switch is slightly dodgy in that the interior light does not always come on when the door is opened. Therefore I am possibly thinking that this may adversely affect the defrost function and the evaporator could have iced up.

However I don’t think this explains the continuous running of the compressor now.

Now what I really want to avoid is calling someone out to fix the fridge and find it cannot be repaired. I have no money at the moment so I would have to take out a loan to pay for this and I don’t want to pay for an engineer *and* a new fridge. I would be very happy if an engineer could repair it for a reasonable cost.

Can anyone give me any hints/opinions to help me with my decision? Please no H&S info – I know this :-). The fridge is about 6 years old.

TIA, Mark.