Mitsubishi Electric PUHY-P250YNW-A Service Handbook page 186

[7-8 Error Code Definitions and Solutions: Codes [6000 - 6999] ]
7-8-18 Error Code [6840]
1. Error code definition
Indoor/outdoor unit communication error
2. Error definition and error detection method
Abnormal if indoor controller board could not receive any signal normally for 6 minutes after turning the power on
Abnormal if indoor controller board could not receive any signal normally for 3 minutes.
Consider the unit as abnormal under the following condition. When 2 or more indoor units are connected to an outdoor unit,
indoor controller board could not receive a signal for 3 minutes from outdoor controller circuit board, a signal which allows
outdoor controller circuit board to transmit signals.
3. Cause, check method and remedy
(1) Contact failure, short circuit or miswiring (converse wiring) of in-
door/outdoor unit connecting wire.
(2) Defective transmitting receiving circuit of outdoor controller cir-
cuit board.
(3) Defective transmitting receiving circuit of indoor controller board.
(4) Noise has entered into indoor/outdoor unit connecting wire.
(5) Defective fan motor
(6) Defective rush current resistor of outdoor power circuit board
7-8-19 Error Code [6841]
1. Error code definition
A control communication synchronism not recover
2. Error definition and error detection method
Indoor/outdoor unit communication error (Outdoor unit)
Abnormal if "0" receiving is detected 30 times continuously though outdoor controller circuit board has transmitted "1".
Abnormal if outdoor controller circuit board could not find blank of transmission path for 3 minutes.
3. Cause, check method and remedy
(1) Indoor/outdoor unit connecting wire has contact failure.
(2) Defective communication circuit of outdoor controller circuit
board.
(3) Noise has entered power supply.
(4) Noise has entered indoor/outdoor unit connecting wire.
BS_07_C
Cause
Cause
Check method and remedy
Check disconnecting or looseness of indoor
/outdoor unit connecting wire of indoor unit or
outdoor unit. Check all the units in case of
twin/triple/quadruple indoor unit system.
Turn the power off, and on again to check. If
abnormality generates again, replace indoor
controller board or outdoor controller circuit
board.
Turn the power off, and detach fan motor
from connector (CNF1). Then turn the power
on again. If abnormality is not displayed, re-
place fan motor. If abnormality is displayed,
replace outdoor controller circuit board.
Check the rush current resistor on outdoor
power circuit board with tester. If open is de-
tected, replace the power circuit board.
Check method and remedy
Check disconnection or looseness of indoor/
outdoor unit connecting wire.
Turn the power off, and on again to check.
Replace outdoor controller circuit board if ab-
normality is displayed again.
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chapter 7 -