Another trick along the same lines as running the fridge on 12V first as a
preheat is to run the fridge on it's lowest setting for about 30 minutes.
You can then turn the fridge to it's coldest setting with no fear of the
flame going out.

If you're already camping and are without an auxiliary battery, this trick
will save you the trouble of having to run the engine to conserve the
battery while you run the fridge on 12V.  Saves you from having to ruin
all that perfectly good silence as well.  At least until the fan kicks on.

Jack