Samsung SR-S22DTC Cooling problem

I have a SR-S22DTC and experiencing the following problems:
The display reads -18 for the freezer and 3 for the fridge. I carried out an reset (power off/on) and the display then read the correct temperatures and the compressor started up. This worked fine until it reached preset temperature few times, I checked and it was warm inside again.
When I have rebooted the fridge it indicated number "3"on the fridge site.
I have contacted the repair serviceman and his conclusion was that the controller board was faulty. He said there either is a compressor relay faulty or there must be something else damaged on the board. I have purchased two relays replacements for the original Fujitsu VSB12TB. This did not change anything for the operation, than I have ordered a new control board DA41-00027A. After 2 weeks waiting period the control board came and it was installed by the repairman, after few hours we have discovered that it did not change anything for the operation of the fridge. what I have discovered that the initialization code changed from "3" to "0". so something have changed, but is very difficult for me to know exactly what is faulty.
I have followed the forum and I think I know where should look for the problems I hope.
I would like to ask thaw for some help, it would be much easier for me to have a service manual for that fridge. If anyone has it I will appreciate
Regards
Jacek