Nice! What is that refrigerator model?
Ok I was able to look that up for you now.
Factory temperature range: 40°F to 66°F
I researched different models to find which one had a smaller step at the bottom rear interior and which had interior dimensions that would fit a large carboy without having to cut doors, add wood spacers to make more interior space, or things of that nature. This model fits a 6 gallon carboy and airlock on top without doing a thing. The only problem with this model (for my purposes) is that the manufacturer limited the temperature setpoint range too tightly.
This is why I added an Emerson Dixell XR30CX temperature controller and rewired the evaporator fans.
With the XR30CX I can adjust the setpoint limits to the absolute limits the refrigeration system can handle.
For example, I could have this fridge cool to well below freezing if I wanted, but this would result in a frozen coil and I'd lose cooling ability (undesirable).
In the end I decided to assign my setpoint boundaries from 31°F to 120°F with a Hysteresis/Differential of 4°F and the evap fans re-wired to run continuously at all times. On an XR30CX the compressor cut-off is at your setpoint and the compressor cut in is "x" degrees above that setpoint as determined by your hysteresis setting (Hy).
With my settings the fridge can now get down to 32°F, instead of the factory limit of 40°F. This can be reached, because I bypassed the factory controllers setpoint boundary and have the evap fans still running during compressor off-cycle (cycle defrost).
The fridge can warm up to 90°F, instead of the factory limit of 66°F. << Through heat generated by evap fan motors and compressor not running.
I have this fridge in the garage, so if the ambient temp was 85°F or higher in the Summer, then the fridge should be able to heat even higher (in the 100's). Interior temps of 100°F+ may not necessarily be needed for fermentation, it would allow for experimentation at these higher temps if so desired.