Mitsubishi Electric Mr.SERVICE PUHZ-HRP71VHA Service Manual page 43

Error Code Abnormal point and detection method
NO ACK signal
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, 6
times continuously.
Note) The address and attribute displayed
at remote controller indicate the con-
troller that did not reply (ACK).
A7
(6607)
2. If displayed address or attribute is out-
door unit, indoor unit detects abnormality
when indoor unit transmits signal to out-
door unit and there was no reply (ACK).
3. If displayed address or attribute is indoor
unit, remote controller detects abnormal-
ity when remote controller transmits sig-
nal to indoor unit and there was no reply
(ACK).
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 transmission
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
transmits signal to indoor unit
while outdoor unit power sup-
ply of one refrigerant system is
turned 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 trouble of 1-5 above,
repair the defect, then turn off the power sup-
ply 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 there was no trouble with 1-5 above in
single refrigerant system (1 outdoor unit),
controller of displayed address or attribute is
defective.
• If there was no trouble with 1-5 above in dif-
ferent refrigerant system (2 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.