Mitsubishi Electric PUHY-HP72 Service Handbook page 185

[7-8 Error Code Definitions and Solutions: Codes [6000 - 6999] ]
7-8-23 Error Code [6843]
1. Error code definition
A control communication start bit detection error
2. Error definition and error detection method
Indoor/outdoor unit communication error
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
1. Error code definition
A control communication start bit detection error
2. Error definition and error detection method
Indoor/outdoor unit communication error (Outdoor unit)
Abnormal if outdoor controller circuit board could not receive anything normally for 3 minutes.
3. Cause, check method and remedy
(1) Contact failure of indoor/outdoor unit connecting wire
(2) Defective communication circuit of outdoor controller circuit
board
(3) Defective communication circuit of indoor controller board
(4) Noise has entered into indoor/outdoor unit connecting wire.
Note: Refer also to the Service Handbook for the indoor units.
64
- chapter 7
Cause
Cause
Check method and remedy
Check disconnecting or looseness of indoor
/outdoor unit connecting wire of all indoor
units or outdoor units.
Turn the power off, and on again to check. If
abnormality generates again, replace indoor
controller board or outdoor controller circuit
board.
Note: other indoor controller board may have
defect.
Turn the power off, and detach fan motor
from connector (CNF1, 2). Then turn the
power on again. If abnormality is not dis-
played, replace 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 of indoor or out-
door units.
Turn the power off, and on again to check.
Replace indoor controller board or outdoor
controller circuit board if abnormality is dis-
played again.
HWE18240_GB