The Fujitsu Halcyon air conditioning system uses flashing light codes displayed on its control panel to signal various problems or errors within the unit. The most common code involves a red light blinking five times consecutively, repeating every two minutes, signaling an issue with the indoor fan motor. Other codes include a single blink accompanied by a beep, indicating a lack of power to the unit. Five blinks followed by four seconds of silence may indicate problems with refrigerant levels or compressor operation. Alternatively, nine blinks could point to communication issues between components.