Mitsubishi Electric PQHY-P72ZLMU-A Service Handbook page 302

[ IX Troubleshooting ]
1. Error Code
6843
A control communication start bit detection error
2. Error definition and error detection method
Indoor/heat source unit communication error (Signal receiving 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 a heat source
unit, indoor controller board could not receive a signal for 3 minutes from heat source controller circuit board, a signal which
allows heat source controller circuit board to transmit signals.
3. Cause, check method and remedy
(1) Contact failure, short circuit or miswiring (converse wiring) of in-
door/heat source unit connecting wire
(2) Defective transmitting receiving circuit of heat source controller
circuit board.
(3) Defective transmitting receiving circuit of indoor controller board.
(4) Noise has entered into indoor/heat source unit connecting wire.
(5) Defective fan motor
(6) Defective rush current resistor of heat source power circuit board
1. Error code definition
A control communication start bit detection error
2. Error definition and error detection method
Indoor/heat source unit communication error (Signal receiving error)
(Heat source unit)
Abnormal if heat source controller circuit board could not receive anything normally for 3 minutes.
3. Cause, check method and remedy
(1) Contact failure of indoor/heat source unit connecting wire
(2) Defective communication circuit of heat source controller circuit
board
(3) Defective communication circuit of indoor controller board
(4) Noise has entered into indoor/heat source unit connecting wire.
HWE15150
Cause
Cause
- 293 -
Check method and remedy
Check disconnecting or looseness of indoor
/heat source unit connecting wire of all indoor
units or Heat source units.
Turn the power off, and on again to check. If
abnormality generates again, replace indoor
controller board or heat source controller cir-
cuit board.
Note: ther 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 heat source controller cir-
cuit board.
Check the rush current resistor on heat
source power circuit board with tester. If
open is detected, replace the power circuit
board.
Check method and remedy
Check disconnection or looseness of indoor/
heat source unit connecting wire of indoor or
heat source units.
Turn the power off, and on again to check.
Replace indoor controller board or heat
source controller circuit board if abnormality
is displayed again.
GB