I have a 10+ year old Samsung french door refrigerator model RF4287HARS.

For quite some time the freezer compartment has not been getting cold enough but the refrigerator seems to be working fine, so I hired a local repair outfit to check it out. They observed that the unit was only getting to 20F but they could get it colder in power freeze mode so they recommended a 24 hour thaw of the unit to clear any ice build up and if that didn't work replacement of the freezer evaporator cover was recommended.

I did the 24 hour thaw out and the unit after a very extended period of time can get to about 10F. Better but still not where it should be (-2F). i went ahead and ordered and replaced the evaporator cover and using my fluke multimeter with a thermistor I read 5F as the best temp I can get even if I program the set point to -8F and turn on power freeze mode.

What other parts could be involved in the problem or is this "as good as it gets" with this model and the age of it?

I have tested the freezer compartment thermistor and it checks out okay (checked resistance by placing it with a meter in a working freezer and verifying ohms value).

With the age of the unit I don't want to keep throwing money at it but a replacement comparable unit will be $3,000 or more so if I can fix it with another part willing to give it a shot.

One oddity I have noticed is that when it is factory reset (long term power off and restart) the panel will show the correct compartment temperature but after a couple of hours it will rapidly adjust to show the set point regardless of what the actual temp in the freezer is. I'm not sure if this is indicative of a board problem where it stops reading resistance properly but if this is likely the culprit would be interested in which part to replace.

Thanks.