05 Sep Communication Error F1 (Sendo SFSU 46K)
1. Check that the connection of the external to the internal unit is correct, otherwise connect the L and N and the communication cable, one by one, between internal and external.
2. Measure if the voltage between the zero line and the communication line is a half-wave signal of 18V-30AV, check if the communication circuit on the external and internal central board has been damaged, otherwise replace it.
3. Check if the LED display on the external power board is active, otherwise replace the electronic control board. Check if the operation of the unit is abnormal due to external interference, and if it is, find it and stop it.