The question For a Venus bound space probe could could a fan be used to prevent overheating? got me thinking.
Most if not all crewed spacecraft have had fans to move air for one reason or another.
However most spacecraft are un-crewed and some have substantial internal volume and lots of electronics. When my imagination runs wild I imagine a small server farm with racks full of electronics, blinking LEDs and the roar of cooling fans.
Of course liquid circulation can cool things, so an atmosphere and fans are probably not necessary.
Question: But have fans ever been used in un-crewed spacecraft?
note: By "un-crewed" I mean spacecraft that were not designed for humans.