Mitsubishi Electric CITY MULTI PUHY-400YMF-C Service Handbook page 138

Phenomena
4 "HO" indication on 1) The M-NET transmission power supply form the
the remote controller
is not lit, and the
ON/OFF switch does
not work.
2) Short circuit of the M-NET transmission line
3) Error wiring of the M-NET transmission line on the
4) M-NET transmission line break on the side of Indoor
5) Loose or disconnection of wiring between the M-NET
6) Error wiring of the MA remote control
7) The unit address is not "00" as it should be with
8) The address of Indoor Unit becomes 51 or more.
9) The master and slave setting of the MA remote
10)Use the M-NET remote control in spite of the
11)Defects for the room controller board (MA remote
12)Defects for the remote controller
Check method and handling
The same
phenomena in all unit of the same
refrigerant system?
YES
Self-diagnosis LED
checks
7120 error display?
NO
Check for 11) item
Factors
available?
NO
Check for 1) item
outdoor unit is not supplied.
1
The original power supply of Indoor Unit is not
turned on.
2
The connector on the controller board in Indoor
Unit is removed.
Main board ----CNS1, CNVCC3
INV board----CNAC2, CNVCC1, CNL2
3
Power supply circuit defects of the outdoor unit.
(For detail, refer to Pages 127)
G INV board defects
G Diode stack defects
Prevention resistance of rush current (R1)
G
damage.
side of the outdoor unit
1
A break of the transmission line or terminal block
removal
2
Indoor Unit transmission line is wired to the
transmission line terminal block (TB7) for central
control by mistake.
Unit (Short/ Open)
transmission terminal block (TB 5) of Indoor Unit and
Indoor Unit controller board CN2M and disconnection of
connectors
1 Short circuit of the MA remote wiring
2 A break of the MA remote control line (No.2) or
disconnection of the terminal block connection
3 Reversed wiring, cross-over in the group control
4 Wire by mistakes the MA remote control to the
terminal block (TB5) for the transmission line
5 Connect by mistakes the M-NET transmission line to
the MA remote control terminal block (TB13)
automatic address setting.
control becomes the slave setting.
automatic address.
communication circuits)
NO
YES
Check for 2) and 3) of
factors
Change the M-NET
YES
remote control to the
-135-
Factors
Check for 4) item
Modify the defective
places
Modify the defective
places
Modify the defective
places
In the case of 2), 3) and 7)
factors, indicate 7102 errors
by the self-diagnosis LED of
the outdoor unit.
Check the terminal
block (TB15) voltage,
the transmission line
of the indoor unit
NO
19 ~ 12V?
YES
Check the items of
5), 6), 8), 9), and 10)
YES
Factors available?
NO
Defects of the indoor
unit controller board or
MA remote control