Daikin FDMQ18WVJU9 User Manual

Troubleshooting for Duct Concealed/Ceiling Cassette Type SiUS122226E
180 Part 6 Service Diagnosis
6.9 Signal Transmission Error (Between Indoor and Outdoor
Unit)
Error Code U4
Method of Error
Detection
The signal transmission data from the outdoor unit is checked whether it is normal.
Error Decision
Conditions
The data sent from the outdoor unit cannot be received normally, or the content of the data is
abnormal.
Supposed
Causes
 Power supply voltage out of specification
 Reduction of power supply voltage
 Wiring error
 Breaking of the connection wires between the indoor and outdoor units (wire No. 3)
 Defective outdoor unit PCB
 Short circuit inside the fan motor winding
 Defective indoor unit PCB
 Disturbed power supply waveform

Daikin FDMQ18WVJU9 Specifications

General

Brand	Daikin
Model	FDMQ18WVJU9
Category	Air Conditioner
Language	English