Yes this fan is to prevent the microwave from overheating. Most microwaves have a thermostat that will turn on the fan if the cooktop area is overheating when it cools the fan will stop.
Since the fan doesn't work anymore, I suggest a replacement. you might be able to use it still but at your own risk, Microwave capacitors hold enough of a charge to act like a grenade when they pop. So for your safety discontinue use.
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The magnetron head contains a Radioactive material that breaks down when explosed to electric to make "rays of microwaves" if that breaks or pops you risk '''Beryllium Oxide''' poisoning from the ceramic insulators
Yes this fan is to prevent the microwave from overheating. Most microwaves have a thermostat that will turn on the fan if the cooktop area is overheating when it cools the fan will stop.
Since the fan doesn't work anymore, I suggest a replacement. you might be able to use it still but at your own risk, Microwave capacitors hold enough of a charge to act like a grenade when they pop. So for your safety discontinue use.
Best Regards,
Sluggy