Mitsubishi Electric City Multi PQHY-P72 Service Handbook page 245

[ IX Troubleshooting ]
2. Transmission error
Error
Error definition and error detec-
Code tion method
6201 Remote controller board failure
An error occurs when the data
cannot be read normally from
the nonvolatile memory built in
on the remote controller.
6202 Remote controller board failure
An error occurs when the clock
function built in on the remote
controller does not work nor-
mally.
6600 Address overlaps
The error is detected when the
same address is transmitted
from different units.
Note: The address/attribute
appeared on the display
on the remote controller
indicates the controller
where an error oc-
curred.
6601 Unset polarity
The error detected when trans-
mission processor cannot dis-
tinguish the polarities of the
M-NET transmission line.
Cause
Remote controller failure
Remote controller failure
Two or more remote controllers for
the heat source units, the indoor
units, LOSSNAY, and the M-NET re-
mote controllers have the same ad-
dresses.
<Example>
The error code 6600 "01" appeared
on the display on the remote control-
ler indicates that an error occurred in
No.1 unit.
Two or more units whose addresses
are 01 exist in the same system.
(1) No voltage is applied to the
M-NET transmission line that
G-50A is connected to.
(2) M-NET transmission line to
which G-50A is connected is
short-circuited.
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Check method and remedy
Replace the remote controller.
Replace the remote controller.
Search for the unit which has the same ad-
dress with that of the source of the trouble.
When the same address is found, turn
off the power of the heat source unit,
LOSSNAY and the indoor unit for 5
minutes or more after changing the ad-
dress, and then turn them on it again.
Check if power is supplied to the M-NET
transmission line of the G-50A, and cor-
rect any problem found.