Genuine Fujitsu 9970055072 Outdoor Solenoid Coil For Reversing Valve is the solenoid coil on the reversing valve in the outdoor unit, which the board energises to switch the system between heating and cooling. When the coil fails the valve cannot change over, so the system can stick in one mode. The genuine part is the one Fujitsu built this outdoor unit around, so it goes back in as the original did.