I'm into a Samsung Refrigerator RSG257AARS that seems not wanting to pull down colder than 21' Degrees in Freezer and 45' Degrees in Refrigerator. Tried running diagnostics but no errors turned up on the display. I've tried all diagnostics but can't seem to get anywhere. I pulled a Vacuum and put new dose of 134a - 7.5 oz. but don't getting cold enough. Should I try new (main and inverter) boards or am I jumping into a open pit? No ERROR DISPLAY for thermistor check when 1st starter either. Any advice would be helpful. Couldn't find Service Manual either just the FAST TRACK.