Johnson control temp control

I purchased a chest freezer and a Johnson controls temp control unit and set everything up. The problem is after the unit hits the desired set point and the compressor turns off, the temperature continues to decrease by up to eight degrees. I am not comfortable with that kind of temp swing. I’m thinking this might change when these is actually a carboy in the freezer, hat having come contents in the freezer with help keep the temp steady.
all advice and comments are welcome.

Thank you.

Here is a post with some ideas. I use the ghetto heating pad method


Dave do you have the temp probe attached to the carboy, or in a thermowell? Or is it freely hanging in the chest freezer? If it is freely hanging, I can almost assure you that your beer is not +/- 8 degrees and it is measuring the actual air temp.

Also, I believe in the settings there is an off-set temp control. I set it to +1.

It’s been awhile for my JC, but I think there are settings in there to prevent such an event.


I see those kind of swings when the probe is hanging in the freezer…right now it’s attached right to the carboy and its doing great at keeping it ± 1 degree of my set temp.

I put my probe in a thin bottle of water to avoid constant cycling and temp swings. Try it.