Mitsubishi Electric PCA Series Service Manual page 23

Abnormal point and detection method
Check code
Pipe temperature thermistor/Condenser-
Evaporator (TH5)
1 The unit is in 3-minute resume protec-
tion mode if short/open of thermistor is
detected. Abnormal if the unit does not
get back to normal within 3 minutes. (The
unit returns to normal operation, if it has
been reset normally.)
2 Constantly detected during cool, dry, and
heat operation (except defrost)
Short: 90°C or more
Open:−40°C or less
P9
Remote controller transmission
error(E0)/signal receiving error(E4)
1 Abnormal if main or sub remote con-
troller cannot receive any transmission
normally from indoor unit of refrigerant
address "0" for 3 minutes.
(Check code: E0)
2 Abnormal if sub remote controller could
not receive any signal for 2 minutes.
(Check code: E0)
1 Abnormal if indoor controller board can
E0 not receive any data normally from
or remote controller board or from other
E4 indoor controller board for 3 minutes.
(Check code: E4)
2 Indoor controller board cannot receive
any signal from remote controller for 2
minutes. (Check code: E4)
Remote controller transmission
error(E3)/signal receiving error(E5)
1 Abnormal if remote controller could not
find blank of transmission path for 6 sec-
onds and could not transmit.
(Check code: E3)
2 Remote controller receives transmitted
data at the same time and compares the
received and transmitted data. Abnormal
if these data are judged to be different
E3
30 continuous times. (Check code: E3)
or
E5
1 Abnormal if indoor controller board could
not find blank of transmission path.
(Check code: E5)
2 Indoor controller board receives trans-
mitted data at the same time and com-
pares the received and transmitted data.
Abnormal if these data are judged to be
different 30 continuous times. (Check
code: E5)
OCH725
Cause
1 Defective thermistor
characteristics
2 Contact failure of connector
(CN29) on the indoor controller
board (Insert failure)
3 Breaking of wire or contact
failure of thermistor wiring
4 Temperature of thermistor is
90°C or more or −40°C or less
caused by defective refrigerant
circuit.
5 Defective indoor controller
board
1 Contact failure at transmission
wire of remote controller
2 All remote controllers are set
as "sub" remote controller.
In this case, E0 is displayed
on remote controller, and E4
is displayed at LED (LED1,
LED2) on the outdoor controller
circuit board.
3 Miswiring of remote controller
4 Defective transmitting receiving
circuit of remote controller
5 Defective transmitting receiving
circuit of indoor controller board
of refrigerant addresses "0".
6 Noise has entered into the
transmission wire of remote
controller.
1 2 remote controllers are set as
"main."
(In the case of 2 remote controllers)
2 Remote controller is connected
with 2 indoor units or more.
3 Repetition of refrigerant
address
4 Defective transmitting receiving
circuit of remote controller
5 Defective transmitting receiving
circuit of indoor controller board
6 Noise has entered into trans-
mission wire of remote control-
ler.
23
Countermeasure
1–3 Check resistance value of thermistor.
For characteristics, refer to (P1).
2 Check contact failure of connector (CN29)
on the indoor controller board.
Refer to "9-7. TEST POINT DIAGRAM".
Turn the power on and check restart after
inserting connector again.
4 Operate in test run mode and check pipe
<condenser/evaporator> temperature with
outdoor controller circuit board. If pipe
<condenser / evaporator> temperature is
extremely low (in cooling mode) or high (in
heating mode), refrigerant circuit may have
defect.
5 Operate in test run mode and check pipe
<condenser / evaporator> temperature with
outdoor control circuit board. If there is
extreme difference with actual pipe
<condenser / evaporator> temperature,
replace indoor controller board.
There is no abnormality if none of above
comes within the unit.
( Turn the power off and on again to operate.
In the case of checking pipe tem-
perature with outdoor controller circuit
board, be sure to connect A-control
service tool (PAC-SK52ST).
1 Check disconnection or looseness of indoor
unit or transmission wire of remote controller.
2 Set one of the remote controllers "main"
if there is no problem with the action above.
3 Check wiring of remote controller.
• Total wiring length: max. 500 m
(Do not use cable with 3 or more cores.)
• The number of connecting indoor units:
max. 16 units
• The number of connecting remote control-
ler: max. 2 units
When it is not the above-mentioned problem of
1–3
4 Diagnose remote controllers.
a) When "RC OK" is displayed,
remote controllers have no problem.
Turn the power off, and on again to check.
If abnormality occurs again, replace
indoor controller board.
b) When "RC NG" is displayed,
replace remote controller.
c) When "RC E3" or "ERC 00-66" is dis-
played, noise may be causing abnormality.
Note:
If the unit is not normal after replacing indoor
controller board in group control, indoor con-
troller board of address "0" may be abnormal.
1 Set a remote controller to main, and the
other to sub.
2 Remote controller is connected with only one
indoor unit.
3 The address changes to a separate setting.
4–6Diagnose remote controller.
a) When "RC OK" is displayed, remote con-
trollers have no problem.
Turn the power off, and on again to check.
When becoming abnormal again, replace
indoor controller board.
b) When "RC NG" is displayed, replace
remote controller.
c) When "RC E3" or "ERC 00–66" is dis-
played, noise may be causing abnormality.
)