The refrigerator is not getting cold. Increased the temperature of both fridge and freezer no change. It appeared that the temp adjustment light display sometimes did not display the temp setting (replaced swicth). The cold air damper/diffuser sometimes does not open up or close right away when the door is open. There is frost build-up on the lower portion of the coils closet to the heater. Checked continuity bewteen both ends of the heater and it read 22 ohms. Cleaned the coils. Not sure of specs for the thermostat and I believe the timer is on the mainboard. Can you provide some suggestions/recommendations

Thank-you

I took the mainboard out and checked to see if something was burnt or any visible problems and put it back in. Took the cover/shelf off of the ice bucket for greater airflow and turned the unit back on. The copper tubes on the lower evaporator coils started frosting up almost immediately and a few minutes later a started hearing a high pitch sound (similar to the emergency broadcast signal). A few hours later the refrigerator actually started to cool again and today it is cooling normally, but I still hear the high pitch sound. Is this due to refrigerant escaping (been making this sound for close to 24hrs) or the compressor going bad

Thank-you

I will check the fan, I did see extra dust on the condensor underneath the fridge, I was able to clean it from the rear, but it'll be a bit harder to get to the dust from the front of the fridge. I will monitor the temps too.