Mitsubishi Electric FRESH MASTER GUF-50RD4 Handbook page 15

Error code Error content
6603 Communication er-
ror (Bus busy error
in the transmission
line)
6606 Communication
error (Handshake
error)
6607 Communication er-
ror (No ACK error)
Cause
The transmission processor cannot
transmit data because short-period volt-
ages such as noise continuously occurs
in the transmission cable line.
Malfunction of a controller for the device
in which the error occurs.
Data was not transmitted correctly due
to an accidental misoperation of the
controller for the device in which the
error occurs.
Malfunction of a controller for the device
in which the error occurs.
(Only when the error occurs in Fresh
Master.)
Single coolant system
1 The address has been changed in
midstream.
2 Improper wiring or disconnection of
the transmission cable
3 Malfunction of the controller
4 Malfunction of the remote controller
(When the switch (SW3-1) is ON)
Group operation system with multiple
coolant lines
1 The above causes 1 to 4
( When Fresh Master is interlocked
with the indoor units in the different
coolant line)
2 Short circuit or disconnection of the
transmission cable to the terminal
block for central control (TB7) in the
outdoor unit
3 The outdoor unit in one of the cool-
ant lines is shut down.
4 The setting of the outdoor unit is
incorrect.
If the error occurs after the unit oper-
ates normally, the following can be
caused.
• Total capacity error (7100)
• Capacity code setting error (7101)
• The number of connected devices er-
ror (7102)
• Address setting error (7105)
Inspect the transmission waveform and
noise in the transmission cable line.
If the controller is normal, it is a malfunc-
tion of the circuit board in Fresh Master.
Replace the circuit board.
Simultaneously turn OFF the power of the
indoor units, Fresh Master, and the outdoor
units, and then, turn them ON again.
If the same error occurs again, it is a mal-
function of the circuit board in the device in
which the error occurs.
Simultaneously turn OFF the power of the
outdoor units and Fresh Master, and then,
turn them ON again.
In the case of the accidental malfunction,
the unit returns to normal.
If the unit does not return to normal, check
the causes 1 to 4.
Simultaneously turn OFF the power of the
outdoor units and Fresh Master, and then,
turn them ON again.
In the case of the accidental malfunction,
the system returns to normal.
If the system does not return to normal,
check the causes 1 to 4.
If none of the above causes applies, check
the error display LEDs of the other remote
controllers or outdoor units.
• When there is an error
See the error code, and repair troubled
sections according to the instructions
described in the troubleshooting.
• When there is no error
It is a malfunction of the circuit board in
Fresh Master.
See the service manual of the outdoor unit.
─ 15 ─
Remedy