Fujitsu · Air to Water Heat Pumps
The hydraulic unit's green LED flashes once and the red LED flashes once, indicating a problem with communication between the indoor hydraulic unit and the outdoor unit. This means the two main parts of your heat pump system are not communicating properly.
Click steps to track your progress.
Stop the heat pump system by disconnecting power, wait at least one minute, then restart the system.
Check all electrical connections between the hydraulic unit and the outdoor unit, ensuring they are secure and correctly wired.
Inspect the area for any equipment generating strong electromagnetic waves that might be interfering with the system's communication.
Verify the power supply voltage to the outdoor unit is between AC 198-264 V at terminals N and L. Consult a qualified technician for voltage checks.
Check the serial signal voltage between terminals 2 and 3 of the outdoor terminal block; it should fluctuate between AC 70 V and AC 130 V. If not, the Main PCB may need replacement by a professional.