Refrigerator advice

[Pleonast]

I have an old (~20 years) Subzero refrigerator that has a strange problem. I can't find the proper power level to maintain the temperature. I'd prefer to keep it about 35-37F. If I set the dial to 5, the temperature stays about 40-45F, too warm. If I set the dial to about 5.5, the temperature stays about 25-30F, too cold.

I've slowly adjusted the dial, making a change in the morning before breakfast and waiting until the next morning to see what the new equilibrium temperature is. I'm assuming that 24 hours is a long enough period for a new dial setting to take effect. There doesn't seem to be happy medium.

The freezer side doesn't seem to have trouble maintaining -10F.

Any suggestions on what could be the problem?

[Sparky812]

I used to have one like this. Isn't your refridgerator side simply cooled by air from the freezer side and the setting dial is just a damper?
Try adjusting the freezer side and see if it effects the fridge. I played with this balancing for a while and I got it.... eventually.

[Pleonast]

Actually, I think the freezer and refrigerator have separate compressors. But I'll adjust the freezer side and see if that has any effect.