you can get fridge/freezers with separate controls for each compartment. If you look at the back you will see two compressors, one for the fridge and one for the freezer. If you read the manufacturer's literature, it will specify the minimum room temperature and this is usually a typical heated room temperature. So, a fridge is unlikely to work properly in a garage in winter and you'd probably have trouble with a freezer too.
You won't see two compressors unless its a really big fridge/freezer. I know someone with an older Westinghouse Fridge/Freezer (mid 90's) with separate controls, it has one compressor. When the fridge gets hot enough, the motor doesn't come on, the fan turns on a blows the freezer air into the fridge (in frost free) and when the freezer gets hot enough, the motor starts and the freezer fan starts. When you open the door during operation, the fan in the compartment you open stops until the door shuts.
If you have a Cyclic, bad luck, as they cannot use two thermostats unless there are two compressors, of the cyclics I've seen, all of them have a single thermostat.
This means, if there is only a thermostat in the fridge, the freezer temperature can change quite a lot, but it receives refrigerant last in Cyclic models, in frost free, there is usually one cooling coil system. On some models though, the fridge is moist and the freezer is frost free, in this case, if there are two thermostats (which is likely) the freezer gets refrigerant first then the fridge, if its one thermostat, the fridge gets the refrigerant first.
I hope this helps you,
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