Thats the air pump, it is a piece of anti-pollution equipment. It only runs for a few minutes upon cold start-up. They are generally considered a replacement only item. The clutch assembly is available seperately. If it's noisy with the engine running after warm-up, it's probably just the clutch assembly. They get alot of money for just the clutch, be sure to price out the whole assembly vs just the clutch, it may be better to replace the whole thing. You may get some comments about repairs being done, by all means feel free to try a repair.
The aux fans run based on either A/C freon pressure (low speed fan) or engine temp (high speed fan). If the A/C is off (incl defroster), then I doubt the fans should be running at 90 degrees, the engine temp has to be I believe at about 100 degrees before the high speed fan comes on. Sounds more like the thermostat or partially plugged radiator is to blame. You can have the area between the A/C condensor and radiator checked for blockage also, it can really fill up with road debris between there.