Mitsubishi Electric Mr.SLIM PU-P71VHA Service Manual page 43

Error Code Meaning of error code and detection method
NO ACK
1. Transmitting side controller detects
abnormal if a message was transmitted
but there is no reply (ACK) that a mes-
sage was received. Transmitting side
detects abnormality every 30 seconds,
six times continuously.
Note) The address and attribute displayed
at remote controller indicate the con-
troller that did not reply (ACK).
2. If displayed address or attribute is out-
door unit, indoor unit detects abnormality
when indoor unit transmitted to outdoor
unit and there was no reply (ACK).
A7
(6607)
3. If displayed address or attribute is indoor
unit, remote controller detects abnormal-
ity when remote controller transmitted to
indoor unit and there was no reply (ACK).
4. If displayed address or attribute is
remote controller, indoor unit detects
abnormality when indoor unit transmitted
to remote controller and there was no
reply (ACK).
OC379F
Case
Common factor that has no rela-
tion with abnormality source.
1 The unit of former address
does not exist as address
switch has changed while the
unit was energized.
2 Extinction of transmission wire
voltage and signal is caused
by over-range transmission
wire.
• Maximum distance ....... 200m
• Remote controller line .... (12m)
3 Extinction of transmission wire
voltage and signal is caused
by type-unmatched transmis-
sion wire.
Type .....
With shield wire-
CVVS, CPEVS
With normal wire (no shield)-
VCTF, VCTFK, CVV
CVS, VVR, VVF, VCT
Diameter ..... 1.25mm
or more
2
4 Extinction of transmission wire
voltage and signal is caused by
over-numbered units.
5 Accidental malfunction of
abnormality-detected controller
(noise, thunder surge)
6 Defective of abnormality-gen-
erated controller
1 Contact failure of transmission
wire of outdoor unit or indoor
unit
2 Disconnection of transmission
connector (CN2M) of outdoor
unit
3 Defective transmitting receiving
circuit of outdoor unit or indoor
unit
1 During group operation with
indoor unit of multi- refrigerant
system, if remote controller
transmit to indoor unit while
outdoor unit power supply of
one refrigerant system is off
or within 2 minutes of restart,
abnormality is detected.
2 Contact failure of transmission
wire of remote controller or
indoor unit
3 Disconnection of transmission
connector (CN2M) of indoor
unit
4 Defective transmitting receiving
circuit of indoor unit or remote
controller
1 During group operation with
indoor unit of multi- refrigerant
system, if indoor unit trans-
mit to remote controller while
outdoor unit power supply of
one refrigerant system is off
or within 2 minutes of restart,
abnormality is detected.
2 Contact failure of transmission
wire of remote controller or
indoor unit
3 Disconnection of transmission
connector (CN2M) of indoor
unit
4 Defective transmitting receiving
circuit of indoor unit or remote
controller
43
Judgment and action
Always try the followings when the error
"A7" occurs.
1 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 mal-
function was accidental, the unit returns to
normal.
2 Check address switch of abnormality-gener-
ated address.
3 Check disconnection or looseness of abnor-
mality-generated or abnormality-detected
transmission wire (terminal block and con-
nector).
4 Check if tolerance range of transmission wire
is not exceeded.
5 Check if type of transmission wire is correct
or not.
If there were some troubles of 1-5 above,
repair the defective, then turn off the power
supply of outdoor unit and indoor unit and
FRESH MASTER or LOSSNAY at the same
time for 2 minutes or more, and turn the power
on again.
• If there was no trouble with 1-5 above in
single refrigerant system (one outdoor unit),
controller of displayed address or attribute is
defective.
• If there was no trouble with 1-5 above in dif-
ferent refrigerant system (two or more outdoor
units), judge with 6.
6 If address of abnormality source is the
address that should not exist, there is the
unit that memorizes nonexistent address
information. Delete useless address informa-
tion with manual setting function of remote
controller.
Only the system FRESH MASTER or
LOSSNAY are connected to, or the system
that is equipped with group setting of differ-
ent refrigerant system.
If there was no trouble with 1-6 above, replace
the controller board of displayed address or
attribute.
If the unit does not return normally, multi-con-
troller board of outdoor unit may be defective
(repeater circuit).
Replace multi-controller board one by one to
check if the unit returns normally.
Continued to the next page.