[rickst29]

The thermostat does have a bulb-tube into the actual refrigerator section (it's mounted on one of the cooling fins). But by mounting it right on one of the fins, in order to protect it from damage, Norcold assures that the measurements will be VERY unreliable.

None of these old-style thermostat bulbs measure accurately in the first place. But the huge problem is the mounting point: If you want to control the refrigerator temperature, then you need to take a measurement in the refrigerated area. (And preferably near the bottom.) Norcold's measurement on the fins presents the status of the bromine-based refrigerant, not the status of your food.

I'm happy with my design of turning the Norcold thermostat to #5 and then letting the new PID controller work via actual temperature. In this design, if the Norcold has some "never go colder than this, EVER" built into it's thermostat, then that will continue to protect the system from damage in extreme conditions.