Jerry, the outside fan for the fridge only comes on when the temperature of the "evaporator?" (I'm never sure what that part of the system is called - but it's a heat ex-changer that transfers heat inside the refrigerator to the outside) gets above a certain level - my fuzzy memory seems to recall 110 degrees. Whatever - it will not run all night but helps to improve the system's performance if it is having to deal with a lot of heat.
I don't recall what the Amp draw of the OEM fan is, I replaced mine with two PC fans that draw less current, are quieter and move more air. I seem to think it was on the order of 1 Amp, but, as I said, it does not run continuously. I think if you take the outside vent screen off (lots of screws), you can get to the fan and its Amp rating is shown on it, if you're really concerned.
- Jack