Originally Posted by RogueGoose85
Im doing a small cup of water with the johnson probe sitting in it. Im thinking that the 2.5 kegerator just has trouble cooling a 5 gallon keg, and 4# co2 tank (small area cramped with stuff?). Im thinking about ditching it and getting a chest freezer.
If you want to drop the temp of the carboy quickly, tape the probe to the side of the carboy and use a blanket to insulate it(or use a thermowell).
The current set up you are using means that once the cup of water(a much smaller volume of liquid than the 5 gallon carboy) reaches the specified temperature the kegerator will turn off and only the ambient air temp of the kegerator is passively cooling the carboy instead of the compressor staying on to actively cool the carboy to your desired temp.
If you have a keg in there as well, be careful not to freeze the beer while you are cold crashing your carboy.