Why would everything be frozen randomly?

So, I came home to grab a beer and the majority of the beer in there and a few bottles of wine are frozen. I keep my CO2 tank in the fridge and have never had any issues. I have a Johnson thermostat and that has never had any issues. I have 2 questions: did the CO2 tank cause this? Would the Johnson thermometer have made it so cold in there on its own because of a short(we did have a storm and maybe it shorted out)? Frustrated because I lost a lot of beer and also because I am not sure what the problem is. Please advise if you have any ideas about how this happened and how I can prevent this from happening in the future?

[quote=“BeaubiWanKenobi”]So, I came home to grab a beer and the majority of the beer in there and a few bottles of wine are frozen. I keep my CO2 tank in the fridge and have never had any issues. I have a Johnson thermostat and that has never had any issues. I have 2 questions: did the CO2 tank cause this? No

Would the Johnson thermometer have made it so cold in there on its own because of a short(we did have a storm and maybe it shorted out)? [color=#0000FF]Probably not. A short would likely destroy the controller. Or blow a fuse inside if there is one.

[/color]Frustrated because I lost a lot of beer and also because I am not sure what the problem is. Please advise if you have any ideas about how this happened and how I can prevent this from happening in the future?[/quote]

Does it appear that the controller is working properly now?

You could try to fiddle with the temp controller on the freezer to make it run warmer, upper 20/low 30’s. That way the beers should only ice a little if something goes haywire.

I believe there is a link in my signature line for that.

How old is the controller? I believe Johnson uses mechanical relays, versus solid state. Over time, old-school relays like this can get stuck on even when the coil is NOT energized. There’s a little spark in the relay when the connections snap on. Over time it can essentially spot weld itself on.
The result is that the controller CAN be leaving the freezer plugged in, without the controller knowing or shorting out.

Open the freezer until the temp is above freezing, but still below your controller set point. If the relay is shot, you will know because the freezer compressor runs even when the controller says it’s off.

My home-made controller has an audible alarm if the temperature swings too far out of range either way, the intent is to signal if there is a stuck relay problem. (I used mechanical relays.) I’m guessing Johnson doesn’t have a similar feature. But with typical relay contacts rated for 10,000 cycles and a freezer that runs ~2x per day, any controller should last decades.