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Troubleshooting
Service manual
34
RXQ25+3 3 3
35AMV1B
Split Sensira R32 BBOP
ESIE21-16 – 2022.02
2.5.27 U4-00 – Indoor/outdoor unit communication problem
Trigger
Effect
Reset
Communication failure
between outdoor and
indoor unit.
Unit will stop operating.
Power reset via outdoor
unit.
To solve the error code
INFORMATION
It is recommended to perform the checks in the listed order.
1
Check if the power supply is compliant with the regulations. See
118].
Possible cause:
▪
Faulty or disturbance of the power supply (power supply MUST be within
range of nominal operating voltage ±4%),
▪
Power drop,
▪
Short circuit.
2
Perform a check of the power supply, connections, wiring,… between the
outdoor unit and the indoor unit. See
Possible cause:
Faulty wiring between the outdoor unit and the indoor unit.
3
Perform a check of the main PCB. See
Possible cause:
Faulty main PCB.
4
Perform a check of the outdoor unit fan motor. See
90].
Possible cause:
Faulty outdoor unit fan motor.
5
Perform a check of the indoor unit main PCB. See
Possible cause:
Faulty indoor unit main PCB.
Prerequisite:
Stop the unit operation via the user interface.
Prerequisite:
Turn OFF the respective circuit breaker.
6
Wait until the rectifier voltage is below 10 V DC.
DANGER: RISK OF ELECTROCUTION
Wait for at least 10 minutes after the circuit breaker has been turned OFF, to be sure
the rectifier voltage is below 10 V DC before proceeding.
7
Check that the thermal interface grease is applied properly on the (PCB or
refrigerant piping) contact surface of the heat sink. Adjust if needed.
Possible cause:
Thermal interface grease NOT applied properly on the heat
sink.
INFORMATION
If all procedures listed above have been performed and the problem is still present,
contact the helpdesk.