My NipponDenso * has no fan / impeller to pull air into * to cool *, so this * ( esp when heated by engine block ) gets too hot ( canboil an egg ) in 33ºC air, output ( ampere & voltage ) drops too low just as described in www.aa1car.com/library/charging_checks.htm last paragraph. Users cannot fit an impeller because no space exists between ( drive belt's ) pulley & * ( like in this web page's photo ). I presume such *'s designers want to keep * small, to fit * into engine compartment, but leaving out an impeller ( & let * overheat , as per this web page ) looks ridiculous. My Hitachi lawn mower's motor has an impeller : motor never gets hot if impeller is fitted. Our 3 Black & Decker trimmers' motors have no impeller, all 3 motors' coils melted in 33ºC air & had to be recoiled.