Daikin VRV IV-S RXTQ-TAVJU Series, Service Manual

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Troubleshooting by Error Code SiUS331604E
195 Service Diagnosis
4.41 Transmission Error between Indoor Units and Outdoor
Units
Error Code
U4
Applicable
Models
All indoor and outdoor units
Method of Error
Detection
Micro-computer checks if transmission between indoor and outdoor units is normal.
Error Decision
Conditions
When transmission is not carried out normally for a certain amount of time
Supposed
Causes
„
Indoor to outdoor, outdoor to outdoor transmission wiring F1, F2 disconnection, short circuit or
wrong wiring
„
Outdoor unit power supply is OFF
„
System address does not match
„
Defective indoor unit PCB
„
Defective outdoor main PCB
Troubleshooting
Be sure to turn off the power switch before connecting or disconnecting
connectors, or parts may be damaged.
Caution
YES
NO
All indoor
unit remote
controllers of the same
refrigerant system
display
U4
.
Is indoor -
outdoor and outdoor -
outdoor unit transmission
wiring normal?
Has
the indoor
or outdoor unit
PCB been replaced,
or has the indoor - outdoor
or outdoor - outdoor unit
transmission wiring
been modified?
NO
YES
Replace the indoor unit PCB
indicated by the error code
U4
.
Fix the indoor-outdoor or
outdoor-outdoor unit
transmission wiring.
NO
YES
Reset the power supply.
Press and hold the RESET
button on the master outdoor
unit PCB for 5 seconds.
∗
The unit will not operate for
up to 12 minutes.
A