Mitsubishi Electric Mr. Slim PUZ-M200YKA2.UK Service Manual page 39

Check Code Abnormal points and detection method
NO ACK signal
Transmitting side controller detects abnormal
if a message was transmitted but there is no
reply (ACK) that a message was received.
Transmitting side detects abnormality every
30 seconds, 6 times continuously.
Note: The address and attribute displayed
at remote controller indicate the
controller that did not reply (ACK).
A7
(6607)
If displayed address or attribute is outdoor
unit, indoor unit detects abnormality when
indoor unit transmits signal to outdoor unit
and there was no reply (ACK).
If displayed address or attribute is indoor
unit, remote controller detects abnormality
when remote controller transmits signal to
indoor unit and there was no reply (ACK).
OCH775B
Cause
Common factor that has no relation
with abnormality source
The unit of former address does
not exist as address switch has
changed while the unit was
energized.
Voltage drop and weak signal
which lead communication
error are caused by over-range
transmission wire.
• Maximum distance ....... 200 m
• Remote controller line .. (12 m)
Voltage drop and weak signal
which lead communication error
are caused by type-unmatched
transmission wire.
Type ......
With shield wire-
CVVS, CPEVS
With normal wire (no shield)-
VCTF, VCTFK, CVV
CVS, VVR, VVF, VCT
Diameter ..... 1.25 mm
or more
2
Voltage drop and weak signal
which lead communication error
are caused by over-numbered
units.
Accidental malfunction of
abnormality-detected controller
(noise, thunder surge)
Defective of abnormality-
generated controller
Contact failure of transmission
wire of outdoor unit or indoor unit
Disconnection of transmission
connector (CN2M) of outdoor unit
Defective transmitting receiving
circuit of outdoor unit or indoor
unit
During group operation with
indoor unit of multi-refrigerant
system, if remote controller
transmits signal to indoor unit
while outdoor unit power supply
of one refrigerant system is
turned off or within 2 minutes of
restart, abnormality is detected.
Contact failure of transmission
wire of remote controller or indoor
unit
Disconnection of transmission
connector (CN2M) of indoor unit
Defective transmitting receiving
circuit of indoor unit or remote
controller
39
Judgment and action
Always try the following when the error
"A7" occurs.
Turn off the power supply of outdoor
unit, indoor unit and FRESH MASTER or
LOSSNAY at the same time for 2 minutes
or more, and turn the power on again. If
malfunction was accidental, the unit returns
to normal.
Check address switch of abnormality-
generated address.
Check disconnection or looseness of
abnormality-generated or abnormality-
detected transmission wire (terminal block
and connector)
Check if tolerance range of transmission
wire is not exceeded.
Check if type of transmission wire is correct
or not.
If the cause of trouble is in –
the defect, then turn off the power supply
of outdoor unit, indoor unit and FRESH
MASTER or LOSSNAY at the same time for
2 minutes or more, and turn the power on
again.
• If the cause of trouble is not in
in single refrigerant system (one outdoor
unit), controller of displayed address or
attribute is defective.
• If the cause of trouble is not in
in different refrigerant system (2 or more
outdoor units), judge with .
If address of abnormality source is the
address that should not exist, there is the
unit that memorizes nonexistent address
information. Delete unused address
information with manual setting function of
remote controller.
This applies only to the system FRESH
MASTER or LOSSNAY is connected to,
or the system that is equipped with group
setting of different refrigerant system.
If the cause of trouble is not any of
– above, replace the controller board of
displayed address or attribute.
If the unit does not return normally, multi
controller board of outdoor unit may be
defective (repeater circuit).
Replace multi controller board one by one to
check if the unit returns normally.
above, repair
– above
– above