Troubleshooting SiBE04-624_B100 Service Diagnosis2.17 Signal Transmission Error (between Indoor Unit andOutdoor Unit)Error Code U4Method of ErrorDetectionThe data sent from the outdoor unit is checked for problem.Error DecisionConditionsThe data sent from the outdoor unit cannot be received without error, or the disable status ofsignal transmission continues for 15 seconds.SupposedCauses Wiring error Breakage of relay wire (transmission wire) Defective outdoor unit PCB Defective fan motor Defective indoor unit PCBTroubleshootingNODoes the distance ofrelay wire exceed30 m?(R18125)YESYESCautionCheck the relay wire between theindoor unit and the outdoor unitfor color and number.Any improper wiring? YESPoor insulationOKAre the relaywires and the earthproperly insulated?Is the measuredvalue 30 to 50 V?YESNONODoes LED A on theoutdoor unit blink?Disconnect No. 3.Measure the voltage betweenNo. 2 and 3 (Apply negativeterminal to No. 2 in DC range)NO(below 30 V or above 50 V)Correct the relay wirebetween the indoor unit andthe outdoor unit.Replace the relay wirebetween the indoor and theoutdoor unit.Distance is to be within thespecified range (30 m orless).Replace the outdoor unitPCB.Replace the indoor unitPCB (Control PCB).Replace the outdoor unitPCB.YESNO Replace both the fan motorand the outdoor unit PCB.Rotate theoutdoor fan by hand.Does the outdoor fan rotatesmoothly?7 sec.VoltagePower on15 sec. StopBe sure to turn off the power switch before connecting or disconnectingconnectors, or parts may be damaged.Check duringthis period Faultdetermined
