Mitsubishi Electric M Series Service Manual page 30

For description of each LED (LED1, 2, 3) provided on the indoor controller, refer to the following table.
LED 1 (power for microcomputer)
LED 2 (power for remote controller)
LED 3 (communication between indoor and outdoor units)
AUTO RESTART FUNCTION
Indoor controller board
This model is equipped with the AUTO RESTART FUNCTION.
When the indoor unit is controlled with the remote controller, the operation mode, set temperature, and the fan speed are memorized by the indoor controller board.
The auto restart function sets to work the moment the power has restored after power failure, then, the unit will restart automatically.
Set the AUTO RESTART FUNCTION using the wireless remote controller. (Mode no.1).
Indicates whether control power is supplied. Make sure that this LED is always lit.
Indicates whether power is supplied to the remote controller. This LED lights only in the case of
the indoor unit which is connected to the outdoor unit refrigerant address "0".
Indicates state of communication between the indoor and outdoor units. Make sure that this LED is
always blinking.
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