An external heat dissipator for a heat generating source having a heat dissipating vent includes a casing adapted to connect to the heat dissipating vent and having an outlet adapted to correspond to and align with the heat generating vent and an inlet communicating with the outlet for allowing air inside the heat generating source to escape therefrom. A fan assembly is securely received in the casing to generate air flow inside the heat generating source for dissipating heat inside the heat generating source. A connection device is provided to engage the casing with the heat dissipating vent of the heat generating source.