I'm sorry, I don't know what it looks like, so can't identify he part to test.
See below click on the picture for more info.
According to the wiring diagram there should be two of them. One for the fresh food and one for the freezer.
I can only find one of them in the parts breakdown item 5 in the Refrigerator Liner section.
Looks like they plug into P4 on the board.
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The sat 24 hrs it has been ok running at 34 degrees consistently. [/COLOR]
This is too cold it should hold the fresh food section around 40 degrees F.
Before that, the thermometer was in ice water. So I had to turn it off overnight. The pattern is it can work ok for a while and then it will go too cold and freeze everything or at other times go too warm and spoil the food.
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Also when I removed the control board I noticed there was a lead not plugged to anything...what is that for?[/COLOR]
I do not know. I cannot see the part side of the board good enough to make out the plug designations.
Something is either wrong with the wiring diagram or the parts breakdown as the diagram shows 2 thermistors but in the breakdown I can only find one.
According to the wiring diagram
P1 is for defrost parts, air baffle position switch, compressor and it's fan and power to the board.
P2 is for the lights, evaporator fan, air baffle motor and ice maker
P4 is for the thermistors.
The thermistors do go bad but it is very, very rare that they will go intermittent which your would have to do to give the symptoms you describe.
I am still leaning towards you received a bad replacement board.
Or the replacement board and the thermistor are bad.
Part number: AP3745265
I was able to find a chart for the thermistor resistances.
It is for a different fridge but the thermistors are the same
Temperature F / Resistance(Ohm)
77.0 / 2700
50.0 / 5348
45.0 / 6033
40.0 / 6989
35.0 / 7916
32.0 / 8750 Freezing point
30.2 / 9216
25.0 / 10483
20.0 / 12269
15.0 / 14019
10.0 / 16497
5.0 / 19474
0. 0 / 22417
–5.0 / 27402
–10.0 / 31717
–15.0 / 37922
Yes it may be time to get in a pro.
I can only summarize what I think.
The unit gets too cold. That tells you that the compressor/sealed system is OK.
In your original post you said you checked the damper so it is opening and closing (not stuck).
So in my opinion it is a temperature control issue and the only parts that do this is the control board and the thermistors. The control board is more likely to go intermittent.