If you notice that the green lights on your Fujitsu air conditioner are flashing, it is likely because there is an error code or diagnostic message being displayed. Depending on the error code, this could be caused by a number of things such as a faulty temperature sensor, dirty filter, blocked condenser coil, low refrigerant levels or even just a power issue. If you can identify the specific error code from the blinking green light pattern then you will be able to contact Fujitsu technical support and they will be able to provide more detailed advice on how to troubleshoot and fix any issues with your air conditioning unit.