Mitsubishi Electric CITY MULTI PUHY-400YMF-B, Service Handbook

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1
2
*1 Check the transformer in accordance with the “TROUBLE SHOOTING” in the indoor unit’s service handbook.
Symptom Cause Checking method & countermeasure
Despite pressing of re-
mote controller switch,
operation does not start
with no electronic
sound.
(No powering signal
appears.)
At about 10 seconds
after turning remote
controller operation
switch ON, the display
distinguishes and the
operation stops.
The cause of 2) and 3) is
displayed with LED monitor
display LED for 7102 error.
1) M-NET transmission power source is not supplied
from outdoor unit.
1 Main power source of outdoor unit is not connected.
2 Slipping off of connector on outdoor unit circuit
board.
Main board : CNS1, CNVCC3
INV board : CNAC2, CNVCC1, CNL2
3 Faulty power source circuit of outdoor unit.
• Faulty INV board,
• Blown fuse (F1 on INV board)
• Broken diode stack
• Broken resistor (R1) for rush current protection
2) Short circuit of transmission line.
3) Erroneous wiring of M-NET transmission line at outdoor unit.
1 Transmission line disconnection or slipping off from terminal block.
2 Erroneous connection of indoor/outdoor transmission line to TB7.
4) Slipping off of transmission wiring at remote controller.
5) Faulty remote controller.
1) Power source is not fed to indoor unit from transformer.
1 Main power source of indoor unit is not turned on.
2 Slipping off of connector (CND, CNT, CN3T) on indoor controller board.
3 Blown fuse on indoor controller board.
4 Faulty or disconnected transformer of indoor unit.
5 Faulty indoor controller board.
3) Faulty outdoor control circuit board or being out of control.
As normal transmission is failed between indoor and outdoor units, outdoor unit model can not be
recognized.
Checking method & countermeasure
Lighting
Check indoor LED3
Lighting?
Check for the change of LED
display by operating dip
switch SW1 for LED monitor
display.
Extinguishing or
unable to confirm
Check indoor unit power
source terminal block voltage
AC 220 ~ 240 V?
Check fuse on
circuit board
Blown?
Check connector slipping
off (CND, CNT, CN3T)
Slipped off?
Check transformer
resistance value
Within rated?
Check LED monitor display
function of outdoor unit
Changed?
Faulty indoor
controller board
YES
YES
YES
YES
NO
NO
NO
*1
NO
Check main power source
of power source wiring.
Check 220 V ~ 240 V
circuit for short circuit
and ground fault.
Improper connector
connection
Check cause of trans-
former disconnection.
• Ground fault on circuit
board
• Ground fault on sensor,
LEV
Check LED monitor display
function after powering outdoor
unit again.
Apply power
source again.
Repair faulty
point.
Changed?
Casual
trouble
Faulty outdoor unit
control circuit board
(2) Trouble and remedy of remote controller
NO
a) Check transmission terminal block of re-
mote controller for voltage.
i) In case of 17 ~ 30 V
→
Faulty network remote controller
ii) In case of less than 17 V
→
See “Transmission Power Circuit
(30 V) Check Procedure”.
YES
YES
NO