There is a thermostat.
Older units use a sensor tube that runs from the inside of the fridge
to the gas valve. When the inside temperature is cold enough, only a pilot flame burns. When the inside temperature rises, the thermostat opens the propane
valve and a larger flame heats the ammonia gas generator
to start the refrigerator
I guess in cold weather you could turn the main propane
valve off and save the amount of propane
it takes to run the pilot light
. But what would be the consequence if you forgot to get it going when the weather warmed?
For newer units, many have electronic controls that eliminate the pilot light
. I can't see where there would be any saving with such a unit to turn the gas off during cold weather. However, I have never owned this type of refrigerator