Daikin FCQ18PVJU - U4 Malfunction of Transmission between Indoor Units and Outdoor Units

SiUS28-902_a Troubleshooting by Indication on the Remote Controller
Troubleshooting 134
3.38 “U4” Malfunction of Transmission between Indoor Units
and Outdoor Units
Remote
Controller
Display
U4
Applicable
Models
AII indoor unit models
RZQ18~30PVJU
Method of
Malfunction
Detection
Microcomputer checks if transmission between indoor and outdoor units is normal.
Malfunction
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 doesn’t match
 Defect of outdoor unit P.C.B.
 Defect of indoor unit P.C.B.