Genuine Fujitsu 9900227012 Outdoor Magnetic Relay 7.5 - 11KW V45 is the magnetic contactor in the outdoor unit, switching the main power to a part on the control board's command. A contactor that sticks or burns out leaves that part stuck on or off, and the system stops working as it should. A genuine Fujitsu part is made to the same design as the original, so it goes back in the way the outdoor unit was built.