From memory, on the B10BLEs and B9s it was a bearing that collapsed and thus engaged the fan drive constantly, not necessarily a defect as the fan is spinning so the engine is always cool but it is certainly more annoying than anything else... I'm not so au fait of the set up on the StreetDeck, could be similar or more likely duff electronics as they're likely to be electric fans on those...
Those B9s make me feel my age, I unwrapped alot of those as an apprentice when they were brand new (removing all the factory cellophane and floor protectors etc) and now they're on their last knockings... Where does time go..!